resource: Let dev_request_mem_region return an error pointer ...

For all users fix or add the error check.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

clocksource: add uemd clocksource ...

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>