module/smcf: Fix build issue caused by missing headers in smcf

This change fixes the compilation issue in SMCF module's
mgi_validate_header.

Signed-off-by: Manoj Kumar Prabakaran <manojkumar.prabakaran@arm.com>
Signed-off-by: Abhishek Rawat <abhishek.rawat@arm.com>