mem: Remove zero page from the end of mem image files

This was required when pages were stored in elf files for
exec. Now we can stop reading it on eof.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/image.h

@@ -195,9 +195,6 @@ struct page_entry {
 	u8	data[PAGE_IMAGE_SIZE];
 } __packed;
 
-#define final_page_va(va)		((va) == ~0LL)
-#define final_page_entry(page_entry)	(final_page_va((page_entry)->va))
-
 struct sa_entry {
 	u64		sigaction;
 	u64		flags;