radv: fix samples_identical return value.

This was returning an inversion, so not doing as it should have.

We need to compare the fmask value with 0, and return the result
from that.

src/amd/common/ac_nir_to_llvm.c

@@ -3410,6 +3410,9 @@ static void visit_tex(struct nir_to_llvm_context *ctx, nir_tex_instr *instr)
 				   txf_address, txf_count, 0xf);
 
 		result = build_tex_intrinsic(ctx, instr, &txf_info);
+
+		result = LLVMBuildExtractElement(ctx->builder, result, ctx->i32zero, "");
+		result = LLVMBuildICmp(ctx->builder, LLVMIntEQ, result, ctx->i32zero, "");
 		goto write_result;
 	}