ASoC: max98926: make max98926_spk_tlv and max98926_current_tlv static

max98926_spk_tlv and max98926_current_tlv are local to the source and do
not need to be in global scope, so make them static.

Cleans up sparse warnings:
symbol 'max98926_spk_tlv' was not declared. Should it be static?
symbol 'max98926_current_tlv' 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>