ARM: s3c24xx: fix unused gta02_configure_pmu_for_charger warning

gta02_configure_pmu_for_charger is only used when CONFIG_PCF50633_ADC
is set, and otherwise we get a warning about an unused symbol:

arch/arm/mach-s3c24xx/mach-gta02.c:158:1: warning: 'gta02_configure_pmu_for_charger' defined but not used [-Wunused-function]
 gta02_configure_pmu_for_charger(struct pcf50633 *pcf, void *unused, int res)

This adds an #ifdef to shut up the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>