[PATCH] x86_64: Check that early arguments are words on their own

We've always had the problem that arguments only did a prefix match,
which resulted e.g.  in noapic and noapictimer getting confused.

Fix the early argument parsing code to always check that arguments are
whole words (except for those that take additional arguments of course)
I factored out the checking code for that while also makes the code
easier to maintain.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>