Replace return 1 ioctl sub-decoder hack with proper flag

Replace return 1 ioctl sub-decoder hack with proper flag

* defs.h (RVAL_IOCTL_PARSED): Introduce new flag for ioctl sub-decoders
* to signalise that they have successfully printed argument.
* ioctl.c (SYS_FUNC(ioctl)): Check for RVAL_IOCTL_PARSED flag, remove
un-set it before returning the value.
* block.c: Use RVAL_IOCTL_PARSED instead of 1.
* btrfs.c: Likewise.
* dm.c: Likewise.
* evdev.c: Likewise.
* file_ioctl.c: Likewise.
* fs_x_ioctl.c: Likewise.
* hdio.c: Likewise.
* loop.c: Likewise.
* mtd.c: Likewise.
* nsfs.c: Likewise.
* print_sg_req_info.c: Likewise.
* ptp.c: Likewise.
* rtc.c: Likewise.
* scsi.c: Likewise.
* sg_io_v3.c: Likewise.
* sg_io_v4.c: Likewise.
* sock.c: Likewise.
* term.c: Likewise.
* ubi.c: Likewise.
* userfaultfd.c: Likewise.
* v4l2.c: Likewise.