power: reset: Remove deprecated APIs usage related to SCM

Remove the scm related deprecated APIs getting
used in poweroff driver. As specially is_scm_armv8()
not supported from scm driver interface.

Change-Id: I6ef5690a6263f26dbe33ba5052bdfd171585081e
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>