MIPS: tune NSQ for MIPS

I observed that overridden silk_noise_shape_quantizer_del_dec is
refactored in C version, and most performance critical parts moved
to separate functions silk_noise_shape_quantizer_short_prediction
and silk_NSQ_noise_shape_feedback_loop.

So let's drop current mips implementation and override only
the critical parts mentioned above.

Signed-off-by: Siarhei Volkau <[email protected]>
Signed-off-by: Jean-Marc Valin <[email protected]>

Author: SiarheiVolkau

silk/NSQ.h

@@ -98,4 +98,8 @@ static OPUS_INLINE opus_int32 silk_NSQ_noise_shape_feedback_loop_c(const opus_in
 #include "arm/NSQ_neon.h"
 #endif
 
+#if defined(__mips)
+#include "mips/NSQ_mips.h"
+#endif
+
 #endif /* SILK_NSQ_H */

silk/NSQ_del_dec.c

@@ -61,9 +61,6 @@ typedef struct {
 
 typedef NSQ_sample_struct  NSQ_sample_pair[ 2 ];
 
-#if defined(FIXED_POINT) && defined(__mips_dsp) && __mips == 32
-#include "mips/NSQ_del_dec_mipsr1.h"
-#endif
 static OPUS_INLINE void silk_nsq_del_dec_scale_states(
     const silk_encoder_state *psEncC,               /* I    Encoder State                       */
     silk_nsq_state      *NSQ,                       /* I/O  NSQ state                           */