[MTD] [MAPS] Blackfin Async Flash Maps

Handle the case where flash memory and ethernet mac/phy are mapped onto
the same async bank

[try #4]
 - drop superfluous casts
 - drop SSYNC() when reading from the flash and rewrite
   bfin_copy_from() to be like bfin_copy_to() so that
   we dont have to handle all the aligned/unaligned cases

[try #3] rename bf5xx-flash to bfin-async-flash
 - move all kconfig board settings into board resources
 - fixup casting style according to lkml feedback
 - rewrite driver so that it can handle arbitrary of
   instances according to the declared platform resources

[try #2]
Remove useless SSYNC() as Will said

[try #1]
The BF533-STAMP does this for example.
All board-specific configuration goes in your board resources file.

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Acked-By: Jörn Engel <joern@logfs.org>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>