scsi: pmcraid: Fix typos

Change "avaibale" and "avaible" to "available".

Link: https://lore.kernel.org/r/20210521082808.1925-1-zuoqilin1@163.com


Signed-off-by: zuoqilin <zuoqilin@yulong.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>