MFC r281828, r289083, r289084, r289091, r289093, r289095, r289097, r289098,
r289104, r289105, r289118: various i2c fixes...

Fix numerous issues in iic(4) and iicbus(4):
--Allow multiple open iic fds by storing addressing state in cdevpriv
--Fix, as much as possible, the baked-in race conditions in the iic
ioctl interface by requesting bus ownership on I2CSTART, releasing it on
I2CSTOP/I2CRSTCARD, and requiring bus ownership by the current cdevpriv
to use the I/O ioctls
--Reduce internal iic buffer size and remove 1K read/write limit by
iteratively calling iicbus_read/iicbus_write
--Eliminate dynamic allocation in I2CWRITE/I2CREAD
--Move handling of I2CRDWR to separate function and improve error handling
--Add new I2CSADDR ioctl to store address in current cdevpriv so that
I2CSTART is not needed for read(2)/write(2) to work
--Redesign iicbus_request_bus() and iicbus_release_bus():
--iicbus_request_bus() no longer falls through if the bus is already
owned by the requesting device. Multiple threads on the same device may
want exclusive access. Also, iicbus_release_bus() was never
device-recursive anyway.
--Previously, if IICBUS_CALLBACK failed in iicbus_release_bus(), but
the following iicbus_poll() call succeeded, IICBUS_CALLBACK would not be
issued again
--Do not hold iicbus mtx during IICBUS_CALLBACK call. There are
several drivers that may sleep in IICBUS_CALLBACK, if IIC_WAIT is passed.
--Do not loop in iicbus_request_bus if IICBUS_CALLBACK returns
EWOULDBLOCK; instead pass that to the caller so that it can retry if so
desired.

Bugfix: Exit the transfer loop if any read or write operation fails. Also,
perform a stop operation on the bus if there was an error, otherwise the
bus will remain hung forever. Consistantly use 'if (error != 0)' style in
the function.

Mostly rewrite the imx i2c driver. This started out as an attempt to fix
one specific problem: the driver didn't check for ACK/NAK after writing a
slave address byte to the bus, and some slaves signal that they are busy
(such as when completing an internal write to flash memory) by sending a
NAK in response to being addressed.

Use IIC_EBUSBSY and IIC_BUSERR status values consistantly across all drivers.
Make it clearer what each one means in the comments that define them.

Add iic2errno(), a helper function to translate IIC_Exxxxx status values to
errno values that are at least vaguely equivelent. Also add a new status
value, IIC_ERESOURCE, to indicate a failure to acquire memory or other
required resources to complete a transaction.

Return only IIC_Exxxx status values from iicbus-layer functions. Most of
these functions are thin wrappers around calling the hardware-layer driver,
but some of them do sanity checks and return an error.

Add a short name, IIC_INTRWAIT, for the common case (IIC_INTR | IIC_WAIT).

Replace a local sx lock that allowed only one client at a time to access
an eeprom device with iicbus_request/release_bus(), which achieves the
same effect and also keeps other i2c slave drivers from clashing on the bus.

MFC r274641, r274644, r274822, r276049:

Allow i2c bus speed to be configured via hints, FDT data, and sysctl.

Implement bus speed setting for OMAP4, AM335x, and imx5/6.

Fix the i2c bus speed divisors for TI OMAP4 and AM335x to give the
advertised 100, 400, and 1000 KHz speeds.

PR: 195009

MFC r274641, r274644, r274822, r276049:

Allow i2c bus speed to be configured via hints, FDT data, and sysctl.

Implement bus speed setting for OMAP4, AM335x, and imx5/6.

Fix the i2c bus speed divisors for TI OMAP4 and AM335x to give the
advertised 100, 400, and 1000 KHz speeds.

PR: 195009