power: supply: twl4030_charger: correct comparision with old current

Driver reads existing current value from two 8-bit registers, but then
compares only one of them with the new 16-bit value.  clang W=1 is also
not happy:

  twl4030_charger.c:243:16: error: variable 'cur_reg' set but not used [-Werror,-Wunused-but-set-variable]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240705113113.42851-2-krzysztof.kozlowski@linaro.orgSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/twl4030_charger.c

@@ -363,7 +363,7 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci)
 	if (status < 0)
 		return status;
 	cur_reg |= oldreg << 8;
-	if (reg != oldreg) {
+	if (reg != cur_reg) {
 		/* disable write protection for one write access for
 		 * BCIIREF */
 		status = twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0xE7,