x86/mm: implement free pmd/pte page interfaces

x86/mm: implement free pmd/pte page interfaces

Implement pud_free_pmd_page() and pmd_free_pte_page() on x86, which
clear a given pud/pmd entry and free up lower level page table(s).

The address range associated with the pud/pmd entry must have been
purged by INVLPG.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: e61ce6ade404e ("mm: change ioremap to set up huge I/O mappings")
Signed-off-by: Toshi Kani <[email protected]>
Reported-by: Lei Li <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>