x86/mm: mod_l<N>_entry() have no need to use __copy_from_user()

x86/mm: mod_l<N>_entry() have no need to use __copy_from_user()

mod_l1_entry()'s need to do so went away with commit 2d0557c5cb ("x86:
Fold page_info lock into type_info"), and the other three never had such
a need, at least going back as far as 3.2.0. Replace the uses by
l<N>e_read_atomic().

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>