go/analysis/passes/asmdecl: define register-ABI result registers for loong64

Fixes golang/go#68041

Change-Id: I04f4f0305e2b15a6fb89809a60a6d62c7176b2a9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/593275
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Tim King <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: abner-chenc

go/analysis/passes/asmdecl/asmdecl.go

@@ -96,7 +96,7 @@ var (
 	asmArchRISCV64  = asmArch{name: "riscv64", bigEndian: false, stack: "SP", lr: true, retRegs: []string{"X10", "F10"}}
 	asmArchS390X    = asmArch{name: "s390x", bigEndian: true, stack: "R15", lr: true}
 	asmArchWasm     = asmArch{name: "wasm", bigEndian: false, stack: "SP", lr: false}
-	asmArchLoong64  = asmArch{name: "loong64", bigEndian: false, stack: "R3", lr: true}
+	asmArchLoong64  = asmArch{name: "loong64", bigEndian: false, stack: "R3", lr: true, retRegs: []string{"R4", "F0"}}
 
 	arches = []*asmArch{
 		&asmArch386,