disk/diskfilter: Don't make a RAID array with more than 1024 disks

disk/diskfilter: Don't make a RAID array with more than 1024 disks

This is "belt and braces" with commit 12e20a6a695f (disk/diskfilter:
Check calloc() result for NULL): we end up trying to use too much memory
in situations like corrupted Linux software RAID setups purporting to
use a huge number of disks. Simply refuse to permit such configurations.

1024 is a bit arbitrary, yes, and I feel a bit like I'm tempting fate
here, but I think 1024 disks in an array (that GRUB has to read to boot!)
should be enough for anyone.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>