[i2c] Remove I2C IOCTLs

Removed add/rm slave and set frequency IOCTL functionality as we
expect to manage devices via board definitions and removed the calls
from the 'i2c' uapp. Also removed the slave irq IOCTLs which is now
unsued. Kept the transfer IOCTL for future app access to I2C
transactions.

ZX-2621 #comment Remove I2C IOCTLs.

Test: Boots on Pixelbook.

Change-Id: I6f0d201ecaf05a47bb88daa958affdf8b5c65c4d

[fdio] Move headers into lib/fdio/...

Change-Id: Ie8d74e716da913bf6e2672c4acf8cd67b4962b7f

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[uapp][status] Use the new MX_OK and MX_ERR_* mx_status_t names

Change-Id: Iaa8c8c12736e49d202c33612b22d2acd528fcf2d

[uapp][i2c] initialize errno to prevent false errors

errno was not being initialized, so the value was only
valid on errors, and undefined for successful strtol
conversions.

Change-Id: I62e23b6439e5c23d91380a7de482d12cd7d359cc

[app][i2c] open i2c device as read/write

Change-Id: I2f89f1f301ea1717fddfa954750ef09b138f2c38

[i2c] Use ioctl wrappers

Change-Id: If7802ba4ecf70d21653023f1b2575c9629dc8bfb

[i2c] Return size of read/write rather than status

Change-Id: If7824999a3ebc65c2a7421522f8168afcb5bf956

[i2c] Refactor i2c ioctl transfer segments

All segment descriptors appear at the beginning of the ioctl in_buf,
rather than being interleaved with write data. This allows easier
reuse of buffers for writes of different sizes, since the
descriptors don't have to move.

Also moved the i2c.h ioctl header to system/public.

Change-Id: I29c10fc7cad1d635c56e15f48ac8bcda4af724a2

[magenta][ddk] normalize ioctl defines

- ioctls are now unique
- ioctls now encode a kind, family, and number
- ioctls that return a handle are of IOCTL_KIND_GET_HANDLE
- remoteio plumbing updated to reflect this
- drivers and ioctl users updated

Change-Id: Ic202cec6336a4915b09e3cbfff5dc6389f397288

[i2c] Split i2c output into multiple lines

Change-Id: I155334b1cda753a777e933d89d0bf6997cdf12a2

[system] align license and license banners with Fuchsia

This adjusts the Magenta userspace code to match the prevailing
license in Fuchsia (three-clause BSD), using the same banner
and license text.

Change-Id: I6b6d79435c5dbaa32027888874849e4f47aaa7be

[system] clang-format all of userspace

Change-Id: I6bb6a9187a4af83ca5c0656f05d89aa3a09fa5fa

[magenta] Initial commit