Remove casting the values returned by memory allocation function.

Coccinelle emits WARNING:

./drivers/message/fusion/mptctl.c:2596:14-31: WARNING: casting value returned by memory allocation function to (SCSIDevicePage0_t *) is useless.
./drivers/message/fusion/mptctl.c:2660:15-32: WARNING: casting value returned by memory allocation function to (SCSIDevicePage3_t *) is useless.

Link: https://lore.kernel.org/r/1596014390-18605-1-git-send-email-liheng40@huawei.comSigned-off-by: Li Heng <liheng40@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>