refactor(arm): simplify early platform setup functions

Refactor `arm_sp_min_early_platform_setup` to accept generic
`u_register_r` values to support receiving firmware handoff boot
arguments in common code. This has the added benefit of simplifying the
interface into common early platform setup.

Change-Id: Idfc3d41f94f2bf3a3a0c7ca39f6b9b0013836e3a
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
6 files changed