lib/sysfs: Fix /dev to /sys node name translation

lib/sysfs: Fix /dev to /sys node name translation

d0dc6c1 introduced translation of /sys names to /dev names, as required
by the kernel linux/drivers/base/core.c: device_get_devnode(). But there
are other places of code that use /dev names in /sys. They need reverse
translation from '/' to '!'.

For example, fdisk -l returns empty list since a22c6eb for device nodes
in subdirectories (used e. g. by cciss driver).

Introduce yet another helper sysfs_dev_name_to_devname() and use it where
appropriate.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>