mfd: rtsx: Fix checkpatch warning

WARNING: Avoid CamelCase: <min_N>
+	u8 N, min_N, max_N, clk_divider;

WARNING: Avoid CamelCase: <max_N>
+	u8 N, min_N, max_N, clk_divider;

Signed-off-by: Wei WANG <wei_wang@realsil.com.cn>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>