ASoC: rt5514: make array rt5514_dai static

The array rt5514_dai is local to the source and does not need to be in
global scope, so make it static.

Cleans up sparse warnings:
symbol 'rt5514_dai' was not declared. Should it be static?

warning: symbol 'rt5514_dai' was not declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mark Brown <broonie@kernel.org>