ARM: efm32: allow uncompress debug output

efm32 has no mach/uncompress.h, but we can trivially use
the fallback to the ll_debug code by just allowing this
option in Kconfig.

Found during randconfig testing.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Uwe Kleine-König <kernel@pengutronix.de>