The do_mknod_internal() is used for creating special file which is
block, character and fifo, most of the code are from debugfs/debugfs.c,
the debugfs/debugfs.c will be modified to use this function.
[YOCTO #4083]
Signed-off-by: Robert Yang <liezhi.yang@windriver.com> Reviewed-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>