checkpatch: enable check for new typedefs

We should strictly check for every new typedef.
Let checkpatch detect them and let developer use
	Checkpatch-ignore: NEW_TYPEDEFS
if it's really needed to add a new typedef.
With this change chackpatch will not complain for typedef on
function's type but only on enum, struct, variable's type.

Change-Id: I644a753e97de877d892af3a0219716f022fb1c59
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8710
Reviewed-by: zapb <dev@zapb.de>
Tested-by: jenkins

.checkpatch.conf

@@ -17,7 +17,6 @@
 --ignore LINE_SPACING
 --ignore LOGICAL_CONTINUATIONS
 --ignore MACRO_WITH_FLOW_CONTROL
---ignore NEW_TYPEDEFS
 --ignore PARENTHESIS_ALIGNMENT
 --ignore PREFER_DEFINED_ATTRIBUTE_MACRO
 --ignore PREFER_FALLTHROUGH