x86: apuv2: remove unused variable

x86: apuv2: remove unused variable

The driver was newly introduced but the version that got merged
produces a harmless compiler warning:

drivers/platform/x86/pcengines-apuv2.c: In function 'apu_board_init':
drivers/platform/x86/pcengines-apuv2.c:211:6: error: unused variable 'rc' [-Werror=unused-variable]

Remove the evidently useless variable.

Fixes: f8eb0235f659 ("x86: pcengines apuv2 gpio/leds/keys platform driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-By: Enrico Weigelt, metux IT consult <info@metux.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>