Staging: hv: osd: add osd_ prefix to global functions

Put a "osd_" prefix on the osd.c functions in order for us to play nicer
in the kernel namespace.

Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>