extcon: cht_wc: add POWER_SUPPLY dependency

The driver fails to link when CONFIG_POWER_SUPPLY is disabled:

x86_64-linux-ld: vmlinux.o: in function `cht_wc_extcon_psy_get_prop':
extcon-intel-cht-wc.c:(.text+0x15ccda7): undefined reference to `power_supply_get_drvdata'
x86_64-linux-ld: vmlinux.o: in function `cht_wc_extcon_pwrsrc_event':
extcon-intel-cht-wc.c:(.text+0x15cd3e9): undefined reference to `power_supply_changed'
x86_64-linux-ld: vmlinux.o: in function `cht_wc_extcon_probe':
extcon-intel-cht-wc.c:(.text+0x15cd596): undefined reference to `devm_power_supply_register'

It should be possible to change the driver to not require this at
compile time and still provide other functions, but adding a hard
Kconfig dependency does not seem to have any practical downsides
and is simpler since the option is normally enabled anyway.

Fixes: 66e31186

 ("extcon: intel-cht-wc: Add support for registering a power_supply class-device")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>