mm/gup_benchmark.c: add additional pinning methods

mm/gup_benchmark.c: add additional pinning methods

Provide new gup benchmark ioctl commands to run different user page
pinning methods, get_user_pages_longterm() and get_user_pages(), in
addition to the existing get_user_pages_fast().

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Keith Busch <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dan Williams <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>