Cygwin: return better inode numbers for block device entries in /proc/sys

Cygwin: return better inode numbers for block device entries in /proc/sys

Commit 3434d35a64736f0b77a12f61784c2caa33ac44cf fixed a problem when
accessing block devices via their /proc/sys/Device entries.  This
changed the way stat info is generated for these devices, resulting
in identical inode numbers for all block devices under /proc/sys/Device.

This patch fixes that by faking a device number for these devices, just as
before.

Fixes: 3434d35a6473 ("Cygwin: Fix access to block devices below /proc/sys.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>