coccinelle: polish FREE_AND_NULL rules

coccinelle: polish FREE_AND_NULL rules

There are two rules for using FREE_AND_NULL in free.cocci, one for
pointer types and one for expressions.  Both cause coccinelle to remove
empty lines and even newline characters between replacements for some
reason; consecutive "free(x);/x=NULL;" sequences end up as multiple
FREE_AND_NULL calls on the same time.

Remove the type rule, as the expression rule already covers it, and
rearrange the lines of the latter to place the addition of FREE_AND_NULL
between the removals, which causes coccinelle to leave surrounding
whitespace untouched.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>