AMDGPU: Remove dead pattern

This is the unsafe conversion pattern, but not guarded by
an unsafe math check. It is also already done in LegalizeDAG.

llvm-svn: 292173

Author: arsenm

llvm/lib/Target/AMDGPU/SIInstructions.td

@@ -438,11 +438,6 @@ def : Pat <
   (V_CVT_F16_F32_e32 $src)
 >;
 
-def : Pat <
-  (f16 (fpround f64:$src)),
-  (V_CVT_F16_F32_e32 (V_CVT_F32_F64_e32 $src))
->;
-
 def : Pat <
   (i32 (fp_to_sint f16:$src)),
   (V_CVT_I32_F32_e32 (V_CVT_F32_F16_e32 $src))