nilfs2: fix 64-bit division operations in nilfs_bmap_find_target_in_group()

nilfs2: fix 64-bit division operations in nilfs_bmap_find_target_in_group()

With the change to make inode->i_ino a u64, the build started failing on
32-bit ARM with:

    ERROR: modpost: "__aeabi_uldivmod" [fs/nilfs2/nilfs2.ko] undefined!

Fix this by using udiv_u64() for the division.

For finding the index into the group, switch to using a bitwise &
operation since that's more efficient. With this change however,
NILFS_BMAP_GROUP_DIV must be a power of two, so add a compile-time
assertion for that.

Fixes: 998a59d371c2 ("treewide: fix missed i_ino format specifier conversions")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202603100602.KPxiClIO-lkp@intel.com/
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260316-iino-u64-v3-2-d1076b8f7a20@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>