mmc: mmci: Reverse IRQ handling for the arm_variant

Commit "mmc: mmci: Handle CMD irq before DATA irq", caused an issue
when using the ARM model of the PL181 and running QEMU.

The bug was reported for the following QEMU version:
$ qemu-system-arm -version
QEMU emulator version 2.0.0 (Debian 2.0.0+dfsg-2ubuntu1.1), Copyright
(c) 2003-2008 Fabrice Bellard

To resolve the problem, let's restore the old behavior were the DATA
irq is handled prior the CMD irq, but only for the arm_variant, which
the problem was reported for.

Reported-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Cc: <stable@vger.kernel.org> # v3.15+
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>