md: fix return value of rdev_size_change()

md: fix return value of rdev_size_change()

commit c26a44ed1e552aaa1d4ceb71842002d235fe98d7 upstream.

When trying to grow an array by enlarging component devices,
rdev_size_store() expects the return value of rdev_size_change() to be
in sectors, but the actual value is returned in KBs.

This functionality was broken by commit
     dd8ac336c13fd8afdb082ebacb1cddd5cf727889
so this patch is suitable for any kernel since 2.6.30.

Signed-off-by: Justin Maggard <jmaggard10@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>