cmd/compile/internal/abi: use clear built-in

Replace for loop with clear, available since Go 1.21.

Change-Id: I949da08b2a11845cc8a02b2639af78835e316970
Reviewed-on: https://go-review.googlesource.com/c/go/+/704879
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Mark Freeman <[email protected]>
Reviewed-by: Sean Liao <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: kolyshkin

src/cmd/compile/internal/abi/abiutils.go

@@ -661,9 +661,7 @@ func (state *assignState) tryAllocRegs(typ *types.Type) []RegIndex {
 func (pa *ABIParamAssignment) ComputePadding(storage []uint64) []uint64 {
 	nr := len(pa.Registers)
 	padding := storage[:nr]
-	for i := 0; i < nr; i++ {
-		padding[i] = 0
-	}
+	clear(padding)
 	if pa.Type.Kind() != types.TSTRUCT || nr == 0 {
 		return padding
 	}