mfd: sm501: Avoid implicit sign extension

Suspicious implicit sign extension where 'reg' (unsigned char) is
promoted in reg << clksrc to int, then sign-extended to unsigned
long. If reg << clksrc is greater than 0x7FFFFFFF, the upper bits
of the result will all be 1.
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/sm501.c

@@ -514,9 +514,9 @@ unsigned long sm501_set_clock(struct device *dev,
 	unsigned long mode = smc501_readl(sm->regs + SM501_POWER_MODE_CONTROL);
 	unsigned long gate = smc501_readl(sm->regs + SM501_CURRENT_GATE);
 	unsigned long clock = smc501_readl(sm->regs + SM501_CURRENT_CLOCK);
-	unsigned char reg;
 	unsigned int pll_reg = 0;
 	unsigned long sm501_freq; /* the actual frequency achieved */
+	u64 reg;
 
 	struct sm501_clock to;