sdhci: Fix "Unexpected interrupt" handling

Whenever a power interrupt is signaled it is also reported as an unexpected
one. All other unexpected interrupts get lost. Cause is a not inversed
bitmask to remove power interrupts from the status.

Signed-off-by: Rolf Eike Beer <eike-kernel@sf-tec.de>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>