x86/mm: Implement common put_data_pages for put_page_from_l[23]e

x86/mm: Implement common put_data_pages for put_page_from_l[23]e

Both put_page_from_l2e and put_page_from_l3e handle having superpage
entries by looping over each page and "put"-ing each one individually.
As with putting page table entries, this code is functionally
identical, but for some reason different.  Moreover, there is already
a common function, put_data_page(), to handle automatically swapping
between put_page() (for read-only pages) or put_page_and_type() (for
read-write pages).

Replace this with put_data_pages() (plural), which does the entire
loop, as well as the put_page / put_page_and_type switch.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>