ALSA: es1938: replace TLV_DB_RANGE_HEAD with DECLARE_TLV_DB_RANGE

Instead of the hard-to-mantain TLV_DB_RANGE_HEAD macro, use
DECLARE_TLV_DB_RANGE, which computes its size automatically.

(Also make this data const on the way.)

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>