Fixes gcc '-Wunused-but-set-variable' warnings:

drivers/power/supply/ab8500_charger.c:
 In function ab8500_charger_init_hw_registers:
drivers/power/supply/ab8500_charger.c:3013:24: warning:
 variable vbup33_vrtcn set but not used [-Wunused-but-set-variable]
drivers/power/supply/ab8500_charger.c:3013:5: warning:
 variable bup_vch_range set but not used [-Wunused-but-set-variable]

Fixes: 4c4268dc ("power: supply: ab8500: Drop AB8540/9540 support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>