cpuidle: drivers: firmware: psci: Dont instrument suspend code

The PSCI suspend code is currently instrumentable, which is not safe as
instrumentation (e.g. ftrace) may try to make use of RCU during idle
periods when RCU is not watching.

To fix this we need to ensure that psci_suspend_finisher() and anything
it calls are not instrumented. We can do this fairly simply by marking
psci_suspend_finisher() and the psci*_cpu_suspend() functions as
noinstr, and the underlying helper functions as __always_inline.

When CONFIG_DEBUG_VIRTUAL=y, __pa_symbol() can expand to an out-of-line
instrumented function, so we must use __pa_symbol_nodebug() within
psci_suspend_finisher().

The raw SMCCC invocation functions are written in assembly, and are not
subject to compiler instrumentation.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230126151323.349423061@infradead.org