PM / Runtime: Fix typo in status comparison causing warning

GCC version 4.5.1 gives the following warning:

drivers/base/power/runtime.c: In function ‘rpm_check_suspend_allowed’:
drivers/base/power/runtime.c:146:25: warning: comparison between ‘enum dpm_state’ and ‘enum rpm_status’

which seems to be a typo in that dev->power.runtime_status
should be compared instead of dev->power.status.

Signed-off-by: Kevin Winchester <kjwinchester@gmail.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>