Staging: remove cowloop driver

The author has found a number of problems with the current version
of this driver in the current kernel, and is reworking it to get
things working again.  Because of that, it would be better to remove
the driver now and add it back in a future kernel release.

Cc: H.J. Thomassen <hjt@ATComputing.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>