osdep/linux/hostdisk: Use stat() instead of udevadm for partition lookup

osdep/linux/hostdisk: Use stat() instead of udevadm for partition lookup

The sysfs_partition_path() calls udevadm to resolve the sysfs path for
a block device. That can be accomplished by stating the device node
and using the major/minor to follow the symlinks in /sys/dev/block/.

This cuts the execution time of grub-mkconfig to somewhere near 55% on
system without LVM (which uses libdevmapper instead sysfs_partition_path()).

Remove udevadm call as it does not help us more than calling stat() directly.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>