armv8: aarch64: Fix the warning about x1-x3 nonzero issue

For 64-bit kernel, there is a warning about x1-x3 nonzero in violation
of boot protocol. To fix this issue, input argument 4 is added for
armv8_switch_to_el2 and armv8_switch_to_el1. The input argument 4 will
be set to the right value, such as zero.

Signed-off-by: Alison Wang <alison.wang@nxp.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: York Sun <york.sun@nxp.com>