md: add MODULE_DESCRIPTION for all md related modules.

Suggested by  Oren Held <orenhe@il.ibm.com>

Signed-off-by: NeilBrown <neilb@suse.de>

diff --cc drivers/md/faulty.c
Simple merge

diff --cc drivers/md/linear.c
Simple merge

diff --cc drivers/md/md.c
Simple merge

diff --cc drivers/md/multipath.c
Simple merge

diff --cc drivers/md/raid0.c
Simple merge

diff --cc drivers/md/raid1.c
Simple merge

diff --cc drivers/md/raid10.c
Simple merge

diff --cc drivers/md/raid5.c
Simple merge

diff --cc drivers/md/raid6algos.c
Simple merge