scsi: mpt3sas: Make MPI2_CONFIG_PAGE_SASIOUNIT_0::PhyData[] a flexible array

scsi: mpt3sas: Make MPI2_CONFIG_PAGE_SASIOUNIT_0::PhyData[] a flexible array

This terminal 1-length variable array can be directly converted into a C99
flexible array member.

As all users of MPI2_CONFIG_PAGE_SASIOUNIT_0 (Mpi2SasIOUnitPage0_t) either
calculate its size without depending on its sizeof() or do not use
PhyData[], no further source changes are required:

 - mpt3sas_config.c:mpt3sas_config_get_number_hba_phys() fetches a
   Mpi2SasIOUnitPage0_t for itself, but does not use PhyData[].

 - mpt3sas_config.c:mpt3sas_config_get_sas_iounit_pg0() fetches a
   Mpi2SasIOUnitPage0_t into a caller-provided buffer, and may fetch and
   write PhyData[] into that buffer depending on its sz argument.  Its
   callers:

   - mpt3sas_scsih.c:_scsih_update_vphys_after_reset(),
     mpt3sas_scsih.c:_scsih_get_port_table_after_reset(),
     mpt3sas_scsih.c:_scsih_sas_host_refresh(),
     mpt3sas_scsih.c:_scsih_sas_host_add(), and
     mpt3sas_transport.c:_transport_phy_enable() all calculate sz
     independently of sizeof(Mpi2SasIOUnitPage0_t) and allocate a
     suitable buffer before calling mpt3sas_config_get_sas_iounit_pg0()
     and using PhyData[].

Signed-off-by: James Seo <james@equiv.tech>
Link: https://lore.kernel.org/r/20230806170604.16143-5-james@equiv.tech
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>