video: remove support for non-existing atmel,at32ap-lcdc in atmel_lcdfb

The AVR32 architecture has been removed from the kernel in commit
26202873

, hence clean out the
atmel,at32ap-lcdc parts in the atmel_lcdfb.c video driver.

AVR32 architecture never supported device tree, hence this code was not
used by anybody.

Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>