r600g/sb: implement r600 gpr index workaround. (v3.1)

r600g/sb: implement r600 gpr index workaround. (v3.1)

r600, rv610 and rv630 all have a bug in their GPR indexing
and how the hw inserts access to PV.

If the base index for the src is the same as the dst gpr
in a previous group, then it will use PV instead of using
the indexed gpr correctly.

The workaround is to insert a NOP when you detect this.

v2: add second part of fix detecting DST rel writes followed
by same src base index reads.

v3: forget adding stuff to structs, just iterate over the
previous node group again, makes it more obvious.
v3.1: drop local_nop.

Fixes ~200 piglit regressions on rv635 since SB was introduced.

Reviewed-By: Glenn Kennard <glenn.kennard@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>