nv50: dynamically allocate space for shader local storage

nv50: dynamically allocate space for shader local storage

Fixes 21 piglit tests:
spec/glsl-1.10/execution/variable-indexing/
fs-temp-array-mat4-index-col-row-wr
vs-temp-array-mat4-index-col-row-wr
vs-temp-array-mat4-index-row-wr

spec/glsl-1.20/execution/variable-indexing/
fs-temp-array-mat3-index-col-row-rd
fs-temp-array-mat3-index-row-rd
fs-temp-array-mat4-col-row-wr
fs-temp-array-mat4-index-col-row-rd
fs-temp-array-mat4-index-col-row-wr
fs-temp-array-mat4-index-row-rd
fs-temp-array-mat4-index-row-wr
vs-temp-array-mat3-index-col-row-rd
vs-temp-array-mat3-index-col-row-wr
vs-temp-array-mat3-index-row-rd
vs-temp-array-mat3-index-row-wr
vs-temp-array-mat4-col-row-wr
vs-temp-array-mat4-index-col-row-rd
vs-temp-array-mat4-index-col-row-wr
vs-temp-array-mat4-index-col-wr
vs-temp-array-mat4-index-row-rd
vs-temp-array-mat4-index-row-wr
vs-temp-array-mat4-index-wr

... and prevents a lot of GPU lockups