acl: Realign struct posix_acl to save 8 bytes

Reduce posix_acl's struct size by 8 bytes by realigning its members.

Cc: Christian Brauner <brauner@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://lore.kernel.org/r/20241015202158.2376-1-thorsten.blum@linux.dev


Signed-off-by: Christian Brauner <brauner@kernel.org>