[PATCH] clean up major_name

[PATCH] clean up major_name

->major_name for per-disk gendisks set to full name - i.e.
IDE gendisks have "hda", "hdb", etc. instead of "hd".
As the result, we kill a lot of crap in check.c::disk_name().
In particular, now we can afford ->minor_shift set to 0
for ide-cd (disk_name() was the only obstacle)