vservices: block: Port virtual block drivers to 4.14

Virtual block drivers are broken for4.14 due to block
level framework primitives change. Port the virtual
block drivers to build and compile for 4.14.

Change-Id: I50808765b4b1bf817db06d523d17fb2a87e80ddc
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>
Signed-off-by: Prakruthi Deepak Heragu <pheragu@codeaurora.org>