The arm64 stacktrace code can be used in kprobe context, and so cannot
be safely probed. Some (but not all) of the unwind functions are
annotated with `NOKPROBE_SYMBOL()` to ensure this, with others markes as
`__always_inline`, relying on the top-level unwind function being marked
as `noinstr`.

This patch has stacktrace.c consistently mark the internal stacktrace
functions as `__always_inline`, removing the need for NOKPROBE_SYMBOL()
as the top-level unwind function (arch_stack_walk()) is marked as
`noinstr`. This is more consistent and is a simpler pattern to follow
for future additions to stacktrace.c.

There should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230411162943.203199-4-mark.rutland@arm.comSigned-off-by: Will Deacon <will@kernel.org>