flash/nor: Add Ambiq Micro Apollo flash driver.

flash/nor: Add Ambiq Micro Apollo flash driver.

Initial release of Ambiq Micro Apollo flash driver
supporting our sub-threshold (low power) Cortex M4F part,
and Evaluation Kit.

We have been shipping openocd to our customers for about one year.

The EVK boards are SWD only using ftdi. We also use two of the
other COM instances to display debug information.

It takes about 15 seconds to flash 512K, and mass erase is
about 5 seconds.

Tested by internal verification group, FAE's, and customer sites.

Merged commit 'refs/changes/17/3417/1' as suggested. Makefile.am
and drivers.c follow the new format to avoid conflicts.

Removed unused fault_capture command.

Added documentation for flash driver.

Change-Id: Iae92d869369c6827244f0071f9cb522d8d91fed8
Signed-off-by: Rick Foos <rfoos@solengtech.com>
Reviewed-on: http://openocd.zylin.com/3230
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>