mmc: mmci: Remove bogus local_irq_save()

On !RT interrupt runs with interrupts disabled. On RT it's in a
thread, so no need to disable interrupts at all.
Remove the local_irq_save() invocation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>