qcom: peripheral-loader: Account for arm64 alignment requirements

ARM64 mandates that 8 byte accesses to/from device memory shall
only be allowed with 64 bit aligned addresses. The current Linux
ARM64 memset implementation does not account for alignment, and
memset_io is inefficient (it does a byte copy).

Until a more generic solution is implemented, account for this
alignement restriction by always passing in 64 bit aligned
address and size parameters to memset().

Change-Id: I2a3647486cc8a86531c79d1af53ba42957dd231b
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>