lib/test_bitmap.c: clean up test_zero_fill_copy() test case and rename

lib/test_bitmap.c: clean up test_zero_fill_copy() test case and rename

Since we have separate explicit test cases for bitmap_zero() /
bitmap_clear() and bitmap_fill() / bitmap_set(), clean up
test_zero_fill_copy() to only test bitmap_copy() functionality and thus
rename a function to reflect the changes.

While here, replace bitmap_fill() by bitmap_set() with proper values.

Link: http://lkml.kernel.org/r/20180109172430.87452-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Yury Norov <ynorov@caviumnetworks.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>