lib/test_bitmap.c: add bitmap_zero()/bitmap_clear() test cases

lib/test_bitmap.c: add bitmap_zero()/bitmap_clear() test cases

Explicitly test bitmap_zero() and bitmap_clear() functions.

Link: http://lkml.kernel.org/r/20180109172430.87452-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Yury Norov <ynorov@caviumnetworks.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>