coccinelle: fix parallel build with CHECK=scripts/coccicheck

The command "make -j8 C=1 CHECK=scripts/coccicheck" produces
lots of "coccicheck failed" error messages.

Julia Lawall explained the Coccinelle behavior as follows:
"The problem on the Coccinelle side is that it uses a subdirectory
with the name of the semantic patch to store standard output and
standard error for the different threads.  I didn't want to use a
name with the pid, so that one could easily find this information
while Coccinelle is running.  Normally the subdirectory is cleaned
up when Coccinelle completes, so there is only one of them at a time.
Maybe it is best to just add the pid.  There is the risk that these
subdirectories will accumulate if Coccinelle crashes in a way such
that they don't get cleaned up, but Coccinelle could print a warning
if it detects this case, rather than failing."

When scripts/coccicheck is used as CHECK tool and -j option is given
to Make, the whole of build process runs in parallel.  So, multiple
processes try to get access to the same subdirectory.

I notice spatch creates the subdirectory only when it runs in parallel
(i.e. --jobs <N> is given and <N> is greater than 1).

Setting NPROC=1 is a reasonable solution; spatch does not create the
subdirectory.  Besides, ONLINE=1 mode takes a single file input for
each spatch invocation, so there is no reason to parallelize it in
the first place.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Julia Lawall <Julia.Lawall@lip6.fr>