arm, am335x: make mpu pll config configurable

upcoming support for siemens boards switches mpu pll clk in board
code. So make this configurable.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@ti.com>
diff --git a/arch/arm/cpu/armv7/am33xx/clock_am33xx.c b/arch/arm/cpu/armv7/am33xx/clock_am33xx.c
index a1efc75..9c4d0b4 100644
--- a/arch/arm/cpu/armv7/am33xx/clock_am33xx.c
+++ b/arch/arm/cpu/armv7/am33xx/clock_am33xx.c
@@ -246,7 +246,7 @@
 		;
 }
 
-static void mpu_pll_config(void)
+void mpu_pll_config_val(int mpull_m)
 {
 	u32 clkmode, clksel, div_m2;
 
@@ -260,7 +260,7 @@
 		;
 
 	clksel = clksel & (~CLK_SEL_MASK);
-	clksel = clksel | ((MPUPLL_M << CLK_SEL_SHIFT) | MPUPLL_N);
+	clksel = clksel | ((mpull_m << CLK_SEL_SHIFT) | MPUPLL_N);
 	writel(clksel, &cmwkup->clkseldpllmpu);
 
 	div_m2 = div_m2 & ~CLK_DIV_MASK;
@@ -274,6 +274,11 @@
 		;
 }
 
+static void mpu_pll_config(void)
+{
+	mpu_pll_config_val(CONFIG_SYS_MPUCLK);
+}
+
 static void core_pll_config(void)
 {
 	u32 clkmode, clksel, div_m4, div_m5, div_m6;