kbuild: kill output in silent mode of mkcompile_h

The mkcompile_h script does `echo` regardless of silent mode the make is
running at, so have it respect $quiet from kbuild and only echo when not in
silent mode.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>