avr32: atmel_default_console_device depends on CONFIG_SERIAL_ATMEL

allnoconfig:

arch/avr32/mach-at32ap/built-in.o: In function `at32_select_gpio':
(.init.text+0x548): undefined reference to `atmel_default_console_device'

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>