mmc: sdio: enable asynchronous interrupt support in 4-bit mode

SDIO 3.0 specification has added the support for asynchronous interrupt
period during which card allows the clock to be gated off. Host needs
to first read the "Support Asynchronous Interrupt" bit in CCCR register
space to check if the card supports the feature or not. If yes and if
the host wants to enable the feature, host needs to write '1' to
"Enable Asynchronous Interrupt" bit in CCCR register space.

This change allows the host controller driver to control whether to enable
the asynchronous interrupt in card or not and if the asynchronous interrupt
is enabled then clock gating feature would be enabled for such cards.

Change-Id: I678cffb63af6a2013640a5eafa6ce9bfad8a51d6
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>