checkpatch: disallow --git and --file/--fix

Don't allow these options to be combined.

Miscellanea:

o Add missing $P: to some die("reason message") output

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/3dc7bdaa58490f5906efc11a4d6113e42a087723.camel@perches.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>