bcm2835-mmc: Fix duplicate free_irq() on remove

The BCM2835 MMC host driver requests its interrupt as a device-managed
resource, so the interrupt is automatically freed after the driver is
unbound.

However on driver unbind, bcm2835_mmc_remove() frees the interrupt
explicitly to avoid invocation of the interrupt handler after driver
structures have been torn down.

The interrupt is thus freed twice, leading to a WARN splat in
__free_irq().  Fix by not requesting the interrupt as a device-managed
resource.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Frank Pavlic <f.pavlic@kunbus.de>