power: supply: bq24257_charger: Replace depends on REGMAP_I2C with select

regmap is a library function that gets selected by drivers that need
it. No driver modules should depend on it. Depending on REGMAP_I2C makes
this driver only build if another driver already selected REGMAP_I2C,
as the symbol can't be selected through the menu kernel configuration.

Fixes: 2219a935 ("power_supply: Add TI BQ24257 charger driver")
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/Kconfig

@@ -577,7 +577,7 @@ config CHARGER_BQ24257
 	tristate "TI BQ24250/24251/24257 battery charger driver"
 	depends on I2C
 	depends on GPIOLIB || COMPILE_TEST
-	depends on REGMAP_I2C
+	select REGMAP_I2C
 	help
 	  Say Y to enable support for the TI BQ24250, BQ24251, and BQ24257 battery
 	  chargers.