scsi: ibmvfc: Use compiler attribute defines instead of __attribute__()

Update ibmvfc.h structs to use the preferred __packed and __aligned()
attribute macros defined in include/linux/compiler_attributes.h in place of
__attribute__().

Link: https://lore.kernel.org/r/20200904232936.840193-1-tyreld@linux.ibm.com


Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>