libavcodec/mips: fix for mips optimized fp fft with hard coded tables disabled

Floating point FFT (nips optimized) breaks when hard coded tables are
not enabled because MIPS optimization of floating point FFT uses only
ff_init_ff_cos_tabs(16) which is not enabled by default in that case.

This patch is fixing it.

Signed-off-by: Nedeljko Babic <nbabic@mips.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>