[block][fvm] remove support for iotxns

Change-Id: Ib0205d4b67269bc9d16ff00533cda6124d2620bd

[dev][block] Drastically simplify BLOCK_CORE protocol

Observations:
- Almost every block device driver implements the protocol
functions (set_callbacks, get_info, read, write) using
nearly identical code.
- The only differences which exist in those functions are
within the read/write functions, which may do additional
boundary checking. However, this boundary checking is
already accomplished by iotxn_queue, so it is redundant.

Exploiting these Observations:
- Relocate the iotxn allocating / enqueueing functionality
into the generic block driver, so it can be shared by
all block device drivers registered as BLOCK_CORE.
- In doing so, there is no longer a need for registered
callbacks. This simplifies block device drivers further.

Change-Id: I795418489cebd3ecebcb2d1153f1cfd7dcc77d5c

[ddk] Remove driver bind() cookie and unbind() callback

Also removed "owner" and "owner_cookie" from internal zx_device_t struct

Adjusted intel-hda audio drivers to create devices to hold driver context
rather than using the driver bind cookie.

Change-Id: I0eca7f6fa3b155be71843291812e7aa9fea5bf55

[zx] Magenta -> Zircon

The Great Renaming is here!

Change-Id: I3229bdeb2a3d0e40fb4db6fec8ca7d971fbffb94

[fvm] Initial commit of Fuchsia VPartition Manager

Change-Id: I1dd488889dd440814277629ffbcfd6d57cf30f47