hwrng: imx-rngc - fix an error path

commit 47a1f8e8 upstream.

Make sure that the rngc interrupt is masked if the rngc self test fails.
Self test failure means that probe fails as well. Interrupts should be
masked in this case, regardless of the error.

Cc: stable@vger.kernel.org
Fixes: 1d544944

 ("hwrng: mx-rngc - add a driver for Freescale RNGC")
Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>