[PATCH] doc: fix kernel-parameters 'quiet'

Fix "quiet" parameter doc.  No trailing '=' sign, no value after it.  And
it disables "most" kernel messages, not all of them.

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>