devfs compile breaks on 2.4.20-pre2

[John Kim]

devfs is seems to be broken for 2.4.20-pre2 because include/linux/genhd.h
has been modified from 2.4.20-pre1.  I see that 'number' member has been
removed from hd_struct in include/linux/genhd.h.

Functions devfs_register_disc and devfs_register_partitions in
fs/partitions/check.c is still expecting "number" it to be there.

Unfortunately I don't know enough about devfs (or kernel in general) to
fix this.  My apologies if this mailing list wrong place to report
problems like this.

John Kim