scsi: megaraid: Remove set but unused variable

In mega_is_bios_enabled(), the variable ret is set but unused. Remove it to
avoid a compiler warning.

Link: https://lore.kernel.org/r/20200706123352.452003-1-damien.lemoal@wdc.com


Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>