staging: comedi: drivers.c: remove unused inline functions

Remove the inline functions uvirt_to_kva and kvirt_to_kva, they
are not referenced by any of the drivers.c code.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>