defconfig: msm: Enable SDHC support flag for sdxpoorwills

Enable CONFIG_MMC_SDHCI_MSM on sdxpoorwills for enabling SDHCI
(Secure Digital Host Controller Interface) on sdxpoorwills.
SDHCI needed for supporting eMMC/SD/SDIO devices.

Change-Id: Ie56395cc14f462c6b5dc950ef500fe90cbb6921f
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>