iio: adc: mcp3911: avoid ambiguity parameters in macros

Name macro parameters after what they represent instead of 'x'
and make sure the evaluation of that will have no side effects.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Link: https://lore.kernel.org/r/20230822192259.1125792-6-marcus.folkesson@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/mcp3911.c

@@ -29,8 +29,8 @@
 #define MCP3911_REG_MOD			0x06
 #define MCP3911_REG_PHASE		0x07
 #define MCP3911_REG_GAIN		0x09
-#define MCP3911_GAIN_MASK(ch)		(GENMASK(2, 0) << 3 * ch)
-#define MCP3911_GAIN_VAL(ch, val)      ((val << 3 * ch) & MCP3911_GAIN_MASK(ch))
+#define MCP3911_GAIN_MASK(ch)		(GENMASK(2, 0) << 3 * (ch))
+#define MCP3911_GAIN_VAL(ch, val)      ((val << 3 * (ch)) & MCP3911_GAIN_MASK(ch))
 
 #define MCP3911_REG_STATUSCOM		0x0a
 #define MCP3911_STATUSCOM_DRHIZ		BIT(12)
@@ -51,8 +51,8 @@
 #define MCP3911_REG_GAINCAL_CH1		0x17
 #define MCP3911_REG_VREFCAL		0x1a
 
-#define MCP3911_CHANNEL(x)		(MCP3911_REG_CHANNEL0 + x * 3)
-#define MCP3911_OFFCAL(x)		(MCP3911_REG_OFFCAL_CH0 + x * 6)
+#define MCP3911_CHANNEL(ch)		(MCP3911_REG_CHANNEL0 + (ch) * 3)
+#define MCP3911_OFFCAL(ch)		(MCP3911_REG_OFFCAL_CH0 + (ch) * 6)
 
 /* Internal voltage reference in mV */
 #define MCP3911_INT_VREF_MV		1200