m32r: remove redundant tests on unsigned

`off' and `max_cpus' are unsigned.  When negative they are wrapped and
caught by the other test.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>