soc: qcom: peripheral-loader: use memset_io() for zeroing device memory

The ARM64's memset() doesn't guarantee pointer aligned write always even
if destination address and size are aligned.  Use memset_io() for ARM64
to avoid potential alignment fault.
ARM32 version of memset() is known as it guarantees pointer aligned writes
always.  Keep memset() for better performance for ARM32.

Change-Id: I504fb2ecf5c87c85b05692c3315afcb51c03c5e0
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>