board: 8226: add gpiomux configuration for SDC3 slot GPIOs

This patch adds the gpiomux configuration for GPIOs of SDC3 slot.
SDCC functionality for these GPIOs are muxed with other
functionalities so before enabling the relevant config options for
SDC3, make sure that current functionality for those GPIOs are
disabled.

CRs-Fixed: 490761
Change-Id: I04dd442399fdad912c79f3b912cae46651e2a4ae
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Krishna Konda <kkonda@codeaurora.org>