Check major number of block device when querying md device

Check major number of block device when querying md device

It give error message when query a non md device.
mdadm /dev/null
/dev/null: is an md device, but gives "Inappropriate ioctl for device" when queried

It's introduced by commit 5cb8599 and 8d0cd09
At first it checks whether a block is md device by function md_get_version.
In this function it does mainly two jobs:
1. send request by ioctl. (now it can be replace by argument ioctlerr)
2. check the block device major number which we don't do this.

We add the second judgement in this patch.

Fixes: 5cb8599 and 8d0cd09
Reported-by: Karsten Weiss <karsten.weiss@atos.net>
Signed-off-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>