[PATCH] Doc/SubmittingPatches cleanups

A few cleanups to SubmittingPatches:
- mention SubmitChecklist
- remove mention of my simple patch script tools
- remove last-updated line

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