working on degraded RAID device (thanks to Christian Schöninger)

If the first physical device of a RAID1 array is faulty or removed, lilo 
fails to install. It doesn't get valid informations about the device 
(md: RAIDset device 0 = 0x0000) and didn't resume with the next disk.
In 'raid.c' lilo should loop through all devices ( for (pass=0; pass < 
raid_limit; pass++) ) to get the disk geometry. But raid_limit is set to 
md_array_info.active_disks ( 1 ) and getting informations about the 
faulty or removed device is skipped. This patch really scans all devices 
to get all required information.
