Revert "mmc: dw_mmc: Don't allow Runtime PM for SDIO cards"

Revert "mmc: dw_mmc: Don't allow Runtime PM for SDIO cards"

This reverts commit a6db2c86033b ("mmc: dw_mmc: Don't allow Runtime PM for
SDIO cards")'

As dw_mmc now is capable of preventing runtime PM suspend while SDIO IRQs
are enabled, let's drop the less fine-grained method, which is preventing
runtime PM suspend for all SDIO cards - no matter of whether SDIO IRQs are
being enabled or not.

In this way we don't keep the host runtime PM resumed, unless it's really
needed, thus avoiding to waste power.

Especially when SDIO IRQs is supported via a separate out-of-band IRQ line,
which isn't defined by the SDIO standard, typically the SDIO func driver
doesn't enable SDIO IRQs via sdio_claim_irq(). So, for these cases we can
now allow the dwmmc device to be runtime PM suspended in-between requests.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>