ALSA: hda/ca0132: make array ca0132_alt_chmaps static

The array ca0132_alt_chmaps is local to the source and does not
need to be in global scope, so make it static.

Cleans up sparse warning:
warning: symbol 'ca0132_alt_chmaps' was not declared. Should it be
static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>