staging: most: cdev: fix chrdev_region leak

staging: most: cdev: fix chrdev_region leak

[ Upstream commit aba258b73101670c06b1dd700e500ed0a3fa0e8e ]

The function unregister_chrdev_region is called with a different counter
as the alloc_chrdev_region. To fix this, this patch introduces the
constant CHRDEV_REGION_SIZE that is used in both functions.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>