staging: usbip: userspace: cleanup makefiles

Remove unneeded comments; change deprecated flag INCLUDE to
AM_CPPFLAGS and put -D option in *_CPPFLAGS; and use "simply
expanded variables" in assignments.

Signed-off-by: matt mooney <mfm@muteddisk.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>