platform: msm8996: Add QUSB ref clock

QUSB ref clock is needed for QUSB phy sequence update

Change-Id: I789d4fa14ddced52836e60272e9e572a11e54c28
diff --git a/platform/msm8996/include/platform/iomap.h b/platform/msm8996/include/platform/iomap.h
index d3ba81a..cd790fc 100644
--- a/platform/msm8996/include/platform/iomap.h
+++ b/platform/msm8996/include/platform/iomap.h
@@ -80,6 +80,7 @@
 
 #define AHB2_PHY_BASE               0x7416000
 #define PERIPH_SS_AHB2PHY_TOP_CFG   (AHB2_PHY_BASE + 0x10)
+#define GCC_RX2_USB2_CLKREF_EN      0x00388014
 
 /* Clocks */
 #define CLK_CTL_BASE                0x300000