x86: include ENTRY/END in entry handlers in entry_64.S

Impact: cleanup of entry_64.S

Except for the order and the place of the functions, this
patch should not change the generated code.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>