WIP: freedreno: we do actually support sqrt
WIP: freedreno/a3xx: a320 workaround for Y=0=BOTTOM rendering
WIP: freedreno/a3xx/compiler: handle some relative addressing constraints... cannot handle const or relative in cat5 and src2 of cat3
WIP: freedreno/a3xx/compiler: relative dst.. TODO I don't think all instructions can have relative destination..
WIP: freedreno/a3xx/compiler: full precision frag shader

Fixes use of full-precision in fragment shader (ie. don't clobber r0.x
since that can be used by future bary instructions for varying fetch).
And makes use of full-precision the default in fragment shader (but can
be overriden via FD_MESA_DEBUG=fraghalf).

Seems like half precision is often not enough for texture coordinates.
The blob compiler is clever enough to keep texture coords in full
precision registers while using half precision for everything else.  But
we aren't quite that clever yet, so better to default to full precision.