gallium: add defines/shader opcode for texture cube map array

gallium: add defines/shader opcode for texture cube map array

This just adds the texture target and capability along
with 3 new opcodes required to support this extension.

As this extension requires some texture opcodes with samp + 5 args,
we need to use another src register, this is only required
for TEX, TXL and TXB opcodes to implement this spec.

TEX2 is required for shadow cube map arrays
TXL2 is required for cube map array sampler + explicit lod
TXB2 is required for cube map array sampler + lod bias

Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>