cxgb4: Add support for new flash parts

Add support for new flash parts identification, and
also cleanup the flash Part identifying and decoding
code.

Based on the original work of Casey Leedom <leedom@chelsio.com>

Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>