arm: dts: socfpga: stratix10: Update MMC smplsel value

This new MMC sample select value is obtained from running
tests on multiple Stratix 10 boards and proven working.

Signed-off-by: Yau Wai Gan <yau.wai.gan@intel.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@intel.com>