mmc: tmio_mmc_core: don't claim spurious interrupts

commit 5c27ff5db1491a947264d6d4e4cbe43ae6535bae upstream.

I have encountered an interrupt storm during the eMMC chip probing (and
the chip finally didn't get detected).  It turned out that U-Boot left
the DMAC interrupts enabled while the Linux driver  didn't use those.
The SDHI driver's interrupt handler somehow assumes that, even if an
SDIO interrupt didn't happen, it should return IRQ_HANDLED.  I think
that if none of the enabled interrupts happened and got handled, we
should return IRQ_NONE -- that way the kernel IRQ code recoginizes
a spurious interrupt and masks it off pretty quickly...

Fixes: 7729c7a2 ("mmc: tmio: Provide separate interrupt handlers")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>