ASoC: atmel: Use IS_ENABLED()

Simplify the ifdef conditions with IS_ENABLED() macro.
No functional changes.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>