mmc: sdhci-msm: Enable EMMC_BOOT_SELECT bit

To operate eMMC in 8 bit mode, need to route the
DATA LINES 4 to 7 (the GPIO lines from 92 to 95) to eMMC.

To route these data lines to eMMC, need to select the
EMMC_BOOT_SELECT bit in TLMM_EBI2_EMMC_GPIO_CFG
register (along with EBI2_BOOT_SELECT bit). Otherwise,
the eMMC will not work in 8 bit mode. If selected only eMMC
boot bit, then the device will not boot from NAND.

Change-Id: Ia6862a1d30b1e984facc1ef4a791b05c1941513e
Signed-off-by: Srinivas Ganji <sringanj@codeaurora.org>