refactor(cpus): convert the Cortex-X1 to use cpu helpers

Change-Id: I0b62fa613eab4a7545408c0da0c05f88f5f28838
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
(cherry picked from commit 1ff96d6da62bd7bbdfa4661f343949278b597bbf)
1 file changed