ac/nir: remove misleading condition

location is never set to INTERP_SAMPLE, and Nicolai comments:
"... that part is misleading. location refers to the base location, not
the final location of the sample, and it can never be INTERP_SAMPLE."

Suggested-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index 823ea42..9c808ef 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -3856,7 +3856,7 @@
 	interp_param = lookup_interp_param(ctx, instr->variables[0]->var->data.interpolation, location);
 	attr_number = LLVMConstInt(ctx->i32, input_index, false);
 
-	if (location == INTERP_SAMPLE || location == INTERP_CENTER) {
+	if (location == INTERP_CENTER) {
 		LLVMValueRef ij_out[2];
 		LLVMValueRef ddxy_out = emit_ddxy_interp(ctx->nir, interp_param);