lib/genalloc.c: change return type to unsigned long for bitmap_set_ll

mainline inclusion
from mainline-v5.12-rc1
commit 0e24465d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7R8MK
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0e24465d3313832e82f8bd9ee2439da1367dd2e5

--------------------------------

Just as bitmap_clear_ll(), change return type to unsigned long
for bitmap_set_ll to avoid the possible overflow in future.

Link: https://lkml.kernel.org/r/20210105031644.2771-1-sjhuang@iluvatar.ai


Signed-off-by: Huang Shijie <sjhuang@iluvatar.ai>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Guo Mengqi <guomengqi3@huawei.com>