loop: mpersify struct loop_info and loop_ioctl function

loop: mpersify struct loop_info and loop_ioctl function

struct loop_info contains fields of type long, so it definitely should
have been mpersified.

* defs.h (loop_ioctl): Remove prototype.
* loop.c (struct_loop_info): New typedef.
Include DEF_MPERS_TYPE(struct_loop_info) and MPERS_DEFS.
(decode_loop_info): Replace struct loop_info with struct_loop_info.
Cast lo_inode, lo_init[0], and lo_init[1] to kernel_ulong_t and print
them using appropriate format specifiers.
(loop_ioctl): Wrap into MPERS_PRINTER_DECL.

Co-authored-by: Dmitry V. Levin <ldv@altlinux.org>