i965/fs: Remove is_valid_3src() checks from emit_lrp.
i965/fs: Remove is_valid_3src() checks from emit_lrp.

The visitor emits MOVs to temporary registers for immediates, so these
never trigger. For further proof, check case ir_triop_fma.

Reviewed-by: Anuj Phogat <e2026475996c48f0b97fd37e84129b3912980428@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler