pm8x41: diff clock control api

Adds an api to control the diff clock.

Change-Id: Id6437a0e2f574378ca1f66142c6f53f903fa9de4
diff --git a/dev/pmic/pm8x41/include/pm8x41_hw.h b/dev/pmic/pm8x41/include/pm8x41_hw.h
index 9c10ab8..c8c83ce 100644
--- a/dev/pmic/pm8x41/include/pm8x41_hw.h
+++ b/dev/pmic/pm8x41/include/pm8x41_hw.h
@@ -105,4 +105,8 @@
 #define LDO_POWER_MODE                        0x45
 #define LDO_EN_CTL_REG                        0x46
 
+/* USB3 phy clock */
+#define DIFF_CLK1_EN_CTL                      0x5746
+#define DIFF_CLK1_EN_BIT                      7
+
 #endif