arm/dt: msm9625: Add AR6004 device.

AR6004 is the dual band 2-stream 802.11n wireless LAN chip for
mobile.  AR6004 is integrated on MDM9625 over SDIO interface.
This patch adds AR6004 device tree node for MDM9625 platform and
it is required for SoftAP operation.

Change-Id: I5d078a37574fcb3758b460348b6abf01a1887c21
Signed-off-by: Pavan Kumar <pavan@codeaurora.org>