cmd/link/internal/loong64: correct the musl dynamic linker path

cmd/link/internal/loong64: correct the musl dynamic linker path

Musl libc already supports loongarch64, the dynamic linker path is the
same as other architectures: /lib/ld-musl-$ARCH.so.1

Ref: https://git.musl-libc.org/cgit/musl/tree/INSTALL#n141

Change-Id: Ie31d4254f6e14a5d634b2a7b5fa4c6270e2c0dc7
Reviewed-on: https://go-review.googlesource.com/c/go/+/569475
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Qiqi Huang <huangqiqi@loongson.cn>