context_tracking: Fix KCSAN noinstr violation

With KCSAN enabled, even empty inline stubs can be out-of-lined.

Force the context_tracking_guest_exit() stub inline.

Fixes the following warnings:

  vmlinux.o: warning: objtool: vmx_vcpu_enter_exit+0x1be: call to context_tracking_guest_exit() leaves .noinstr.text section
  vmlinux.o: warning: objtool: svm_vcpu_enter_exit+0x85: call to context_tracking_guest_exit() leaves .noinstr.text section

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/dc93f45abdec90c171108b4b590b7fff5790963c.1681320026.git.jpoimboe@kernel.org