arm64: entry: consolidate entry/exit helpers

arm64: entry: consolidate entry/exit helpers

To make the various entry/exit helpers easier to understand and easier
to compare, this patch moves all the entry/exit helpers to be adjacent
at the top of entry-common.c, rather than being spread out throughout
the file.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20210802140733.52716-2-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>