Variable pg_size is set to '0x100 << pg_size', but this value is never read
and it is not used later on. Hence it is a redundant assignment and can be
removed.

Clean up the following clang-analyzer warning:

drivers/target/sbp/sbp_target.c:1264:3: warning: Value stored to
'pg_size' is never read [clang-analyzer-deadcode.DeadStores].

Link: https://lore.kernel.org/r/1620902977-57076-1-git-send-email-jiapeng.chong@linux.alibaba.comReported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>