cogl-pipeline-fragend-arbfp: Fix the comparison for dot3 arguments
cogl-pipeline-fragend-arbfp: Fix the comparison for dot3 arguments

There was a typo in fragend_arbfp_args_equal so that it wasn't
comparing the constants correctly.

Thomas Wood found this bug with static analysis.

spatulasnout/cogl,spatulasnout/cogl,djdeath/cogl,gcampax/cogl,djdeath/cogl,Distrotech/cogl,collects/cogl,gcampax/cogl,djdeath/cogl,djdeath/cogl-android,djdeath/cogl-android,Distrotech/cogl,collects/cogl,gcampax/cogl,Distrotech/cogl,Distrotech/cogl,gcampax/cogl,djdeath/cogl-android