arm64: entry: style cleanup for ARM64_REG_REBALANCE_ON_CTX_SW

The style used by 4fe343f9 ("arm64: entry: add support for
CONFIG_ARM64_REG_REBALANCE_ON_CTX_SW") is inconsistent with other code
in the same file. Clean this up by using tabs instead of spaces, and
lower-case instead of upper-case instructions. No functional change
is expected.

Change-Id: Ia0d27e8b96fbde18f1c77f0728205a8e4109c114
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>