mmc: au1xmmc: propagate errors from platform_get_irq()

The driver overrides the error codes returned by platform_get_irq() to
-ENODEV. Switch to propagating the error codes upstream.

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Tested-by: Manuel Lauss <manuel.lauss@gmail.com>
Link: https://lore.kernel.org/r/f642ef4d-6027-eb2e-0257-1c4f13911aed@omp.ru


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>