Double precision arithmetic in LFE

A number of double precision operations are used in LFE PLC functions, file ivas_lfe_plc.c.

Consider to use a single precision arithmetic.

Then:

• \ivas-codec\lib_enc\ivas_lfe_enc.c(167): shift = (int16_t) floor( IVAS_LFE_SHIFTS_PER_DOUBLE * log2_f( max_value / lfe_abs_sum ) ); -> floorf()