plat/sgi: refactor SDEI specific macros

The macros specific to SDEI defined in the sgi_base_platform_def.h are
not applicable for all the platforms supported by plat/sgi. So refactor
the SDEI specific macros into a new header file and include this file on
only on platforms it is applicable on.

Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>
Change-Id: I0cb7125334f02a21cae1837cdfd765c16ab50bf5
5 files changed