Staging: hv: Get rid of an unnecessary check in blkvsc_probe()

It is never the case that the dev_add function pointer will not be set
(we set it in this code!). Get rid of this meaningless check.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>