lib: test_bitmap: add tests for "N" alias

commit 99c58d1a in linux-rcu.

These are copies of existing tests, with just 31 --> N.  This ensures
the recently added "N" alias transparently works in any normally
numeric fields of a region specification.

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>