crypto: omap-sham - Check for return value from pm_runtime_get_sync

Function pm_runtime_get_sync could fail and we need to check return
value to prevent kernel crash.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>