Going through the code, HAP, EPT, PoD and ALTP2M depend on HVM code.
Put these components under CONFIG_HVM. This further requires putting
one of the vm event under CONFIG_HVM.

Altp2m requires a bit more attention because its code is embedded in
generic x86 p2m code.

Also make hap_enabled evaluate to false when !CONFIG_HVM. Make sure it
evaluate its parameter to avoid unused variable warnings in its users.

Also sort items in Makefile while at it.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 xen/arch/x86/mm/Makefile         | 11 ++++++-----
 xen/arch/x86/mm/mem_access.c     | 18 +++++++++++++++++-
 xen/arch/x86/mm/mem_sharing.c    |  2 ++
 xen/arch/x86/mm/p2m.c            | 23 ++++++++++++-----------
 xen/common/vm_event.c            |  2 ++