scsi: mpt3sas: Fix out-of-bounds compiler warning

scsi: mpt3sas: Fix out-of-bounds compiler warning

I'm facing this warning when building for the parisc64 architecture:

drivers/scsi/mpt3sas/mpt3sas_base.c: In function ‘_base_make_ioc_operational’:
drivers/scsi/mpt3sas/mpt3sas_base.c:5396:40: warning: array subscript ‘Mpi2SasIOUnitPage1_t {aka struct _MPI2_CONFIG_PAGE_SASIOUNIT_1}[0]’ is partly outside array bounds of ‘unsigned char[20]’ [-Warray-bounds]
 5396 |             (le16_to_cpu(sas_iounit_pg1->SASWideMaxQueueDepth)) ?
drivers/scsi/mpt3sas/mpt3sas_base.c:5382:26: note: referencing an object of size 20 allocated by ‘kzalloc’
 5382 |         sas_iounit_pg1 = kzalloc(sz, GFP_KERNEL);
      |                          ^~~~~~~~~~~~~~~~~~~~~~~

The problem is, that only 20 bytes are allocated with kmalloc(), which is
sufficient to hold the bytes which are needed.  Nevertheless, gcc complains
because the whole Mpi2SasIOUnitPage1_t struct is 32 bytes in size and thus
doesn't fit into those 20 bytes.

This patch simply allocates all 32 bytes (instead of 20) and thus avoids
the warning. There is no functional change introduced by this patch.

While touching the code I cleaned up to calculation of max_wideport_qd,
max_narrowport_qd and max_sata_qd to make it easier readable.

Test successfully tested on a HP C8000 PA-RISC workstation with 64-bit
kernel.

Link: https://lore.kernel.org/r/YpZ197iZdDZSCzrT@p100
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>