mm: add SECTION_ALIGN_UP() and SECTION_ALIGN_DOWN() macro

mm: add SECTION_ALIGN_UP() and SECTION_ALIGN_DOWN() macro

Add SECTION_ALIGN_UP() and SECTION_ALIGN_DOWN() macro which aligns given
pfn to upper section and lower section boundary accordingly.

Required for the latest memory hotplug support for the Xen balloon driver.

Signed-off-by: Daniel Kiper <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>