net: rmnet_data: Add support for user defined device name prefix

Run-time user space components can now specify virtual network device
name prefix at device creation. This will be used to support legacy
data services.

CRs-Fixed: 555507
Change-Id: Id34c2761f2060e66b05c521304d5151620ba5665
Signed-off-by: Harout Hedeshian <harouth@codeaurora.org>