x86/altp2m: merge p2m_set_altp2m_mem_access and p2m_set_mem_access

x86/altp2m: merge p2m_set_altp2m_mem_access and p2m_set_mem_access

The altp2m subsystem in its current form duplicates much of the existing
code present in p2m for setting mem_access permissions. In this patch we
consolidate the two versions but keep the separate MEMOP and HVMOP interfaces.

Signed-off-by: Tamas K Lengyel <tlengyel@novetta.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Acked-by: Ian Campbell <    ian.campbell@citrix.com    >
Reviewed-by: George Dunlap <george.dunlap@citrix.com>