Staging: hv: osd.h: remove GUID typedef

GUID should not be a typedef.  As proof of the problem of typedefs,
look, we are passing 2 of these as a value in functions!  Bah...

Cc: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>