x86/shadow: Rework trace_shadow_emulate_other() as sh_trace_gfn_va()

x86/shadow: Rework trace_shadow_emulate_other() as sh_trace_gfn_va()

sh_trace_gfn_va() is very similar to sh_trace_gl1e_va(), and a rather shorter
name than trace_shadow_emulate_other().

It's only referenced in CONFIG_HVM=y builds, so give it a __maybe_unused to
placate randconfig builds.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-Acked-By: Oleksii Kurochko <oleksii.kurochko@gmail.com>