scsi: megaraid_sas: Replace one-element array with flexible-array member in MR_DRV_RA...

scsi: megaraid_sas: Replace one-element array with flexible-array member in MR_DRV_RAID_MAP

One-element arrays are deprecated, and we are replacing them with flexible
array members instead. So, replace one-element array with flexible-array
member in struct MR_DRV_RAID_MAP and refactor the code accordingly.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Link: https://lore.kernel.org/r/1448f387821833726b99f0ce13069ada89164eb5.1660592640.git.gustavoars@kernel.org
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Enhanced-by: Kees Cook <keescook@chromium.org> # Change in struct MR_DRV_RAID_MAP_ALL