avidec: make print_tag() a macro and remove related ifdefs

The dprintf macro is a no-op if DEBUG is not defined, so there
is no need to guard it here.

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 6081f8c4e283bf1b33e4cf4b2ca44217219f9210)
