LiftoffCompiler::ProcessParameter assumed that by processing parameters
in the order of their index, register parameters get
processed first, and that for processing stack parameters it can already
use all registers as temp registers. This is not true with reference
type parameters, because registers always first get assigned to value
type parameters even when there is a reference type parameter with a
lower index. Because of this incorrect assumption register parameters
were overwritten by reference type parameters on the stack that got
processed first.

With this CL, only those registers get used as temp registers for
reference type parameters that are not used for parameters.

CC=jkummerow@chromium.org, clemensb@chromium.org
R=thibaudm@chromium.org

Bug: v8:11596
Change-Id: I30ed7f073147df0bd81b9ef4d2b2a54d7badc937
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2784560
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73635}