The fixed-point decoder actually does not use the floating-point
tables initialized by ff_aac_tableinit() at all. So don't
initialize them for it; instead merge initializing these tables
into ff_aac_float_common_init() which is already the function
for the common static initializations of the floating-point
AAC decoder and the (also floating-point) AAC encoder.
Doing so saves also one AVOnce.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>