coccinelle: tests: improve odd_ptr_err.cocci

The original version only considered the case where the then branch
contains only one call to PTR_ERR.  Reimplement the whole thing to allow
multiple calls, with potentially different arguments.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Michal Marek <mmarek@suse.cz>