PM: base: power: don't try to use non-existing RTC for storing data

PM: base: power: don't try to use non-existing RTC for storing data

commit 0560204b360a332c321124dbc5cdfd3364533a74 upstream.

If there is no legacy RTC device, don't try to use it for storing trace
data across suspend/resume.

Cc: <stable@vger.kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20210903084937.19392-2-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>