r600: fix textures

We weren't allocating enough gprs for the fragment shader
in some cases.  There are likely other issues that still need
to be sorted out for textures, but at least they now work.

src/mesa/drivers/dri/r600/r700_fragprog.c

@@ -299,7 +299,7 @@ GLboolean r700SetupFragmentProgram(GLcontext * ctx)
 
     ui = (r700->SPI_PS_IN_CONTROL_0.u32All & NUM_INTERP_mask) / (1 << NUM_INTERP_shift);
 
-    ui = ui ? ui : unNumOfReg;
+    ui = (unNumOfReg < ui) ? ui : unNumOfReg;
 
     SETfield(r700->ps.SQ_PGM_RESOURCES_PS.u32All, ui, NUM_GPRS_shift, NUM_GPRS_mask);