mm: reuse DEFINE_SHOW_ATTRIBUTE() macro

mm: reuse DEFINE_SHOW_ATTRIBUTE() macro

...instead of open coding file operations followed by custom ->open()
callbacks per each attribute.

[[email protected]: add tags, fix compilation issue]
Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Andy Shevchenko <[email protected]>
Reviewed-by: Matthew Wilcox <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Reviewed-by: Sergey Senozhatsky <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Nitin Gupta <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>