Documentation: SubmittingDrivers: fix Linus's git tree URL

Change resource URL to new git tree -
(http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git

).

Signed-off-by: Ralf Thielow <ralf.thielow@googlemail.com>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>