MX5: fix warning in clock.c

Patch fix warnings compiling with ELDK-4.2:

clock.c: In function 'get_standard_pll_sel_clk':
clock.c:341: warning: 'freq' may be used uninitialized in this function

Reported-by : Marek Vasut <marex@denx.de>
Signed-off-by: Stefano Babic <sbabic@denx.de>

arch/arm/cpu/armv7/mx5/clock.c

@@ -338,7 +338,7 @@ static u32 get_ipg_per_clk(void)
 /* Get the output clock rate of a standard PLL MUX for peripherals. */
 static u32 get_standard_pll_sel_clk(u32 clk_sel)
 {
-	u32 freq;
+	u32 freq = 0;
 
 	switch (clk_sel & 0x3) {
 	case 0: