board: 8974: add SD card detect gpiomux configuration

On MSM8974 platforms, MSM GPIO is used for SD card detect but it's
gpiomux configuration is not specified under gpiomux table. This
patch adds the correct gpiomux configuration for SD card detect GPIO

Change-Id: Ia955b0bc3a7540485f33405dd81340e25fafed2c
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>