ANDROID: KVM: arm64: Add Ftrace trampolines for pKVM hyp

In preparation for supporting Ftrace in the pKVM hypervisor, add two
trampolines. The first one intends to trace function entries. It saves
the caller states before jumping into __hyp_ftrace_trace(). It is
expected from the latter to return the link register.

That LR can then either be the orignal caller parent, or our second
trampoline __hyp_ftrace_ret_tramp. This trampoline is calling
__hyp_ftrace_ret_trace() which can trace function returns and must
restore the original LR value.

Bug: 357781595
Change-Id: I9327d15d8c69ff94c9dbff2806a145de29af308b
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>