mesa/st: Fix image selection for blit soruces.
If the texture hasn't yet been validated, the current tex image contents may have been ignored in favor of the texture's main miptree. Fixes test failure on softpipe in:
Cc: mesa-stable
If the texture hasn't yet been validated, the current tex image contents may have been ignored in favor of the texture's main miptree. Fixes test failure on softpipe in:
Cc: mesa-stable