coccicheck: Allow for overriding spatch flags

Documentation/coccinelle.txt suggests using the SPFLAGS
make variable to pass additional options to spatch.

Reorder the way SPFLAGS is added to FLAGS, to allow
for options in the SPFLAGS to override the default
--very-quiet option.

Similarly, rearrage the FLAGS for org or report mode.
This allows for overriding of the default --no-show-diff
option through SPFLAGS.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: Gilles Muller <Gilles.Muller@lip6.fr>
Acked-by: Nicolas Palix <nicolas.palix@imag.fr>
Acked-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Michal Marek <mmarek@suse.com>