cmd/compile: update loong64 CALL* ops

cmd/compile: update loong64 CALL* ops

allow the loong64 CALL* ops to take variable number of args

Update #40724

Co-authored-by: Xiaolin Zhao <zhaoxiaolin@loongson.cn>
Change-Id: I4706d9651fcbf9a0f201af6820c97b1a924f14e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/521781
Auto-Submit: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Meidan Li <limeidan@loongson.cn>
Reviewed-by: David Chase <drchase@google.com>