freedreno/ir3: start on indirect gpr reads

freedreno/ir3: start on indirect gpr reads

Handle TEMP[ADDR[]] src registers by generating a fanin to group array
elements, similarly to how texture fetch instructions work.

NOTE:
For all the scalar instructions generated for a single tgsi vector
operation which uses an array src (or possibly even uses the same array
as multiple srcs), re-use the same fanin node.  Since a vector operation
operates on all components at the same time, it should never see more
than one version of the same array.

Signed-off-by: Rob Clark <robclark@freedesktop.org>