scsi: ibmvscsis: Increase INITIAL_SRP_LIMIT to 1024

The adapter request_limit is hardcoded to be INITIAL_SRP_LIMIT which is
currently an arbitrary value of 800. Increase this value to 1024 which
better matches the characteristics of the typical IBMi Initiator that
supports 32 LUNs and a queue depth of 32.

This change also has the secondary benefit of being a power of two as
required by the kfifo API. Since, Commit ab9bb631

 ("Partially revert
"kfifo: fix kfifo_alloc() and kfifo_init()"") the size of IU pool for each
target has been rounded down to 512 when attempting to kfifo_init() those
pools with the current request_limit size of 800.

Link: https://lore.kernel.org/r/20220322194443.678433-1-tyreld@linux.ibm.com
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>