staging: comedi: comedi.h: tweak start of header comment

The wording at the start of the header comment is a bit misleading,
particularly the part in parentheses: "(installed as
/usr/include/comedi.h)".  This version of "comedi.h" certainly won't be
installed as that pathname.  Fix it.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>