The fields and APIs in old 'struct memory_ops' are used to add/modify/delete
page table (page or entry). So rename 'struct memory_ops' to 'struct pgtable'.
Tracked-On: #5830
Signed-off-by: Li Fei1 <fei1.li@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>