scsi: myrb: Make symbols DAC960_{LA/PG/PD/P}_privdata static

This symbol is not used outside of myrb.c, so we can mark it static.

Link: https://lore.kernel.org/r/20210327073156.1786722-1-liushixin2@huawei.com


Signed-off-by: Shixin Liu <liushixin2@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>