cmd/compile: don't clobber LR for tail calls

When doing a tail call the link register is live as the callee
will directly return to the caller (of the function that does the
tail call). Don't allocate or clobber the link register.

Fixes #49032.

Change-Id: I2d60f2354e5b6c14aa285c8983a9786687b90223
Reviewed-on: https://go-review.googlesource.com/c/go/+/358435


Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>