clk: mmp: add fixed clock UBS_PLL for pxa910/pxa168

USB will drive clock from USB_PLL.

Signed-off-by: Chao Xie <chao.xie@marvell.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
diff --git a/include/dt-bindings/clock/marvell,pxa168.h b/include/dt-bindings/clock/marvell,pxa168.h
index 79630b9..84ce5de 100644
--- a/include/dt-bindings/clock/marvell,pxa168.h
+++ b/include/dt-bindings/clock/marvell,pxa168.h
@@ -19,6 +19,7 @@
 #define PXA168_CLK_PLL1_2_1_5		19
 #define PXA168_CLK_PLL1_3_16		20
 #define PXA168_CLK_UART_PLL		27
+#define PXA168_CLK_USB_PLL		28
 
 /* apb periphrals */
 #define PXA168_CLK_TWSI0		60