[BNX2]: Add firmware decompression

Add functions to decompress firmware before loading to the internal
CPUs. Compressing the firmware reduces the driver size significantly.

Added file name length sanity check in the gzip header to prevent
going past the end of buffer [suggested by DaveM].

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>