Documentation: PM: Clarify pm_runtime_resume_and_get() return value

Update the documentation to match the behaviour of the code.

pm_runtime_resume_and_get() always returns 0 on success, even if
__pm_runtime_resume() returns 1.

Fixes: 2c412337 ("PM: runtime: Add documentation for pm_runtime_resume_and_get()")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Link: https://patch.msgid.link/20241203143729.478-1-paul.barker.ct@bp.renesas.com


[ rjw: Subject and changelog edits, adjusted new comment formatting ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>