fix(spmd): coverity scan issues

Coverity defects fixed by this patch are:
*** CID 400208:  Performance inefficiencies  (PASS_BY_VALUE)
/include/services/el3_spmd_logical_sp.h: 108 in
ffa_partition_info_regs_get_last_idx()

*** CID 400207:  Performance inefficiencies  (PASS_BY_VALUE)
/services/std_svc/spmd/spmd_logical_sp.c: 359 in
ffa_partition_info_regs_get_part_info()

Signed-off-by: Raghu Krishnamurthy <raghu.ncstate@gmail.com>
Change-Id: I9597377a8ec3d5519995e1619d99ee7102f33939
3 files changed