MIPS: dspr2: added optimization for ColorIndexInverseTransforms

Change-Id: I5b6094ce489d4f896bc4b8f575142eb3c5054beb
Slightly faster lossless decoding (1%)

-> introduce special case 64b pattern-copy, similar to the 8b one for alpha.
-> use mempcy() for non-overlapping areas
+ cosmetics and homogenezation of the code

Change-Id: I0e65e04b96fec94c009a4614137dfba2a0f98561
Merge "Slightly faster lossless decoding (1%)"
MIPS: dspr2: added optimization for TransformDC

Change-Id: Iee69758f6442ea9c80ddaa32cea8d00dda4c6252
MIPS: dspr2: added optimization for TransformAC3

Change-Id: Icd789ee5f6d764297e7dc0a0f8a3bc47ab92ac65