net: rmnet_data: remove NOARP flags for the virtual net device

When IFF_NOARP flag is set for a device, the kernel automatically
sets the accept_dad flag to -1 even though autoconf is enabled.
As a result, nodes on that link were not receiving neighbour
solicitations. Removed the setting of IFF_NOARP during net device
setup.

CRs-Fixed: 629099
Change-Id: Ia8b5d1163196cc0518a20beba643930b4f439771
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>