spm-mm: fix MISRA C-2012 Rule 2.3 spm_mm_boot_info_t defined but never used.

Following merge of patchset [1] the spm_mm_boot_info_t structure is
included in few platform files unconditionally even when SPM_MM option
is disabled.

[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/2647

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I68bc034c9348b5d9bcfd2e5217b781df5ad1b369
3 files changed