crypto: omap-aes - add error check for pm_runtime_get_sync

The AES driver currently assumes that pm_runtime_get_sync will always
succeed, which may not always be true, so add error handling for the
same.

This scenario was reported in the following bug:
place.  https://bugzilla.kernel.org/show_bug.cgi?id=66441

Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>