mwl8k: Adding support for 8764 4x4 AP

The patch does the following:-

a Add entry in the PCIe table
b Add firmware support with API versioning
c Reuse most of the 8366 code
d Make 8764 specific changes where 8764 differs
  from 8366 e.g. structure definitions.

Signed-off-by: Nishant Sarmukadam <nishants@marvell.com>
Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>