MIPS: DSPr2: Added mips_dspr2_blt and mips_dspr2_fill routines.

MIPS: DSPr2: Added mips_dspr2_blt and mips_dspr2_fill routines.

Performance numbers before/after on MIPS-74kc @ 1GHz

Referent (before):

lowlevel-blt-bench:
              src_n_0565 =  L1: 238.14  L2: 233.15  M: 57.88 ( 77.23%)  HT: 53.22  VT: 49.99  R: 47.73  RT: 24.79 (  91Kops/s)
              src_n_8888 =  L1: 190.19  L2: 187.57  M: 28.94 ( 77.23%)  HT: 27.91  VT: 27.33  R: 26.64  RT: 14.68 (  77Kops/s)
cairo-perf-trace:
[ # ]  backend                         test   min(s) median(s) stddev. count
[ # ]    image: pixman 0.25.1
[  0]    image         gnome-system-monitor  268.460  269.712   0.22%    6/6

Optimized:

lowlevel-blt-bench:
              src_n_0565 =  L1:1081.39  L2: 258.22  M:189.59 (252.91%)  HT: 60.23  VT: 55.01  R: 53.44  RT: 23.68 (  89Kops/s)
              src_n_8888 =  L1: 653.46  L2: 113.55  M:135.26 (360.86%)  HT: 38.99  VT: 37.38  R: 34.95  RT: 18.67 (  84Kops/s)
cairo-perf-trace:
[ # ]  backend                         test   min(s) median(s) stddev. count
[ # ]    image: pixman 0.25.1
[  0]    image         gnome-system-monitor  246.565  246.706   0.04%    6/6