checkpatch: add --fix option for ASSIGN_IN_IF

checkpatch: add --fix option for ASSIGN_IN_IF

Add a --fix option for 2 types of single-line assignment in if statements

	if ((foo = bar(...)) < BAZ) {
expands to:
	foo = bar(..);
	if (foo < BAZ) {
and
	if ((foo = bar(...)) {
expands to:
	foo = bar(...);
	if (foo) {

if statements with assignments spanning multiple lines are
not converted with the --fix option.

if statements with additional logic are also not converted.

e.g.:	if ((foo = bar(...)) & BAZ == BAZ) {

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Link: http://lkml.kernel.org/r/9bc7c782516f37948f202deba511bc95ed279bbd.camel@perches.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>