rtc: max31335: Fix comparison in max31335_volatile_reg()

Clang warns (or errors with CONFIG_WERROR=y):

    drivers/rtc/rtc-max31335.c:211:36: error: use of logical '||' with constant operand [-Werror,-Wconstant-logical-operand]
      211 |         if (reg == MAX31335_TEMP_DATA_MSB || MAX31335_TEMP_DATA_LSB)
          |                                           ^  ~~~~~~~~~~~~~~~~~~~~~~
    drivers/rtc/rtc-max31335.c:211:36: note: use '|' for a bitwise operation
      211 |         if (reg == MAX31335_TEMP_DATA_MSB || MAX31335_TEMP_DATA_LSB)
          |                                           ^~
          |                                           |
    1 error generated.

This clearly should be a comparison against reg. Fix the comparison so
that max31335_volatile_reg() does not always return true.

Closes: ClangBuiltLinux#1980
Fixes: dedaf03 ("rtc: max31335: add driver support")
Signed-off-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexandre Belloni <[email protected]>

Author: nathanchance

drivers/rtc/rtc-max31335.c

@@ -208,7 +208,7 @@ static bool max31335_volatile_reg(struct device *dev, unsigned int reg)
 		return true;
 
 	/* temperature registers */
-	if (reg == MAX31335_TEMP_DATA_MSB || MAX31335_TEMP_DATA_LSB)
+	if (reg == MAX31335_TEMP_DATA_MSB || reg == MAX31335_TEMP_DATA_LSB)
 		return true;
 
 	return false;