board: samarium: add SD card detect gpiomux configuration

On msmsamarium platforms, a MSM GPIO is used for SD card detect and it's
gpiomux configuration needs to be set to a specified value for the
SD card to be detected across all platforms. This patch adds the correct
gpiomux configuration for SD card detect GPIO to properly detect SD card
across all platforms.

Change-Id: I83a8bf764458358c604e5926617baff8e03134ca
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>