xen: Fix {set,clear}_foreign_p2m_mapping on autotranslating guests

xen: Fix {set,clear}_foreign_p2m_mapping on autotranslating guests

Commit 82616f9599a7 ("xen: remove tests for pvh mode in pure pv paths")
removed the check for autotranslation from {set,clear}_foreign_p2m_mapping
but those are called by grant-table.c also on PVH/HVM guests.

Cc: <[email protected]> # 4.14
Fixes: 82616f9599a7 ("xen: remove tests for pvh mode in pure pv paths")
Signed-off-by: Simon Gaiser <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>