[PATCH] README update from the stone age

We have no options which the user can set in the Makefile.  Only the
EXTRAVERSION, which is also useful in place of the "backup modules"
suggestion.

We don't have configuration options in the top Makefile.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>