ARM: s3c24xx: fix gta02 build error

The gta02 has always been broken in the case when CONFIG_PCF50633_ADC
is not used, since gta02_charger_worker then passes a nonexisting
variable into the pcf50633_mbc_usb_curlim_set() function.

This addresses the obvious typo by using the variable that is
used everywhere else in this file.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Cc: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Ben Dooks <ben-linux@fluff.org>