bnx2x: Remove many sparse warnings

Remove most of the sparse warnings in the bnx2x compilation
(i.e., thus resulting when compiling with `C=2 CF=-D__CHECK_ENDIAN__').

Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>