ASoC: mediatek: mt2701: Fix -Wunused-const-variable warnings

sound/soc/mediatek/mt2701/mt2701-afe-common.h:66:27: warning:
 mt2701_afe_backup_list defined but not used [-Wunused-const-variable=]

mt2701_afe_backup_list is only used in mt2701-afe-pcm.c,
so just move the definition over there.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190822143747.20944-1-yuehaibing@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>