mpt3sas: set num_phys after allocating phy[] space

In _scsih_sas_host_add, the number of HBA phys are determined and then
later used to allocate an array of struct _sas_phy's.  If the routine
sets ioc->sas_hba.num_phys, but then fails to allocate the
ioc->sas_hba.phy array (by kcalloc error or other intermediate
error/exit path), ioc->sas_hba is left in a dangerous state: all readers
of ioc->sas_hba.phy[] do so by indexing it from 0..ioc->sas_hba.num_phys
without checking that the space was ever allocated.

Modify _scsih_sas_host_add to set ioc->sas_hba.num_phys only after
successfully allocating ioc->sas_hba.phy[].

Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>