BACKPORT: arm64: kernel: Adopt new alternative assembler macros

Convert the dynamic patching for ARM64_WORKAROUND_845719 over to
the newly added alternative assembler macros.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Bug: 31432001
Change-Id: I64444bd26a8d603a9e2b06c994aff94b27061139
(cherry picked from commit e28cabf12304717b1054d0a02f0850f91e8a2074)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>