[dev.typeparams] runtime: fix newproc arg size on ARM

At runtime startup it calls newproc from assembly code to start
the main goroutine. runtime.main has no arguments, so the arg
size should be 0, instead of 8.

While here, use clearer code sequence to open the frame.

Change-Id: I2bbb26a83521ea867897530b86a85b22a3c8be9d
Reviewed-on: https://go-review.googlesource.com/c/go/+/321957


Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>