[SCSI] sd: udev accessing an uninitialized scsi_disk field results in a crash

	sd_probe() calls class_device_add() even before initializing the
sdkp->device variable. class_device_add() eventually results in the user mode
udev program to be called. udev program can read the the allow_restart
attribute of the newly created scsi device. This is resulting in a crash as
the show function for allow_restart (i.e sd_show_allow_restart) returns the
attribute value by reading the sdkp->device->allow_restart variable. As the
sdkp->device is not initialized before calling the user mode hotplug helper,
this results in a crash.
	The patch below solves it by calling class_device_add() only after the
necessary fields in the scsi_disk structure are initialized properly.

Signed-off-by: Nagendra Singh Tomar <nagendra_tomar@adaptec.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>