mmc: sdhci: convert to new SDIO IRQ handling

Use a generic threaded interrupt handler for SDIO interrupt handling,
rather than allowing the SDIO core code to buggily spawn its own
thread.  This results in host drivers to be more in control of how
SDIO interrupts are acknowledged in the hardware, rather than having
the internals of the SDIO core placed upon them, possibly resulting
in sub-standard handling.

At least one SDHCI implementation specifies a very specific sequence
to deal with a card interrupt.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Markus Pargmann <mpa@pengutronix.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>