padata: add parenthesis in MAX_SEQ_NR macro

MAX_SEQ_NR is used in padata_alloc_pd() like this:

        pd->max_seq_nr = (MAX_SEQ_NR / num_cpus) * num_cpus - 1;

It needs parenthesis or the divide by num_cpus takes precedence over the
subtraction.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>