qcom: spm_devices: register spm platform driver at arch initcall.

As no more board file support for 64bit, initialize the
spm driver at arch init level to ensure dependent drivers can use
spm driver functionality during early boot.

Change-Id: I0243c2c2003d23e3b5cc8de7ab1f65d1f2588b6d
Signed-off-by: Anji Jonnala <anjir@codeaurora.org>