ARM: dts: msm: Add WLAN SDIO vdd-xtal for sdxpoorwills

vdd-xtal is removed during bring-up phase and these's
no side effect at that time. However SDIO function enable
timeout is now seen during stability and stress test.

Thus fix it by adding back WLAN SDIO vdd-xtal power supply.

Change-Id: I3f02aebbd384497a79e3f8b7b9a62c2c96944e61
Signed-off-by: jiad <jiad@codeaurora.org>