[PATCH] kbuild: allow multi-word $M in Makefile.modpost

Some people want to do crazy things like pass multiple directories as the
value of $(SUBDIRS) or $M.  Mostly this kinda works, except that
Makefile.modpost constructs a modpost commandline which fails modpost's
argument parsing.  This patch fixes that little wrinkle.

Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>