mmc: sdhci-msm: Remove MMC_CAP2_ASYNC_SDIO_IRQ_4BIT_MODE capability

This removes direct enabling of MMC_CAP2_ASYNC_SDIO_IRQ_4BIT_MODE
capability from sdhci-msm driver.
This capablity needs to be enabled based on reading HOST_CAPABILITIES
register.

Change-Id: I74c2877d5906ee9e2180fdb8d50167af6d03b3af
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>