net: qualcomm: rmnet: memset before sending genl response

Ensure that the generic netlink response has a memset payload
before sending to userspace.

Change-Id: Ie2fa92ce80bb3c0716e779cebeaedb2d31d759c1
Acked-by: Ryan Chapman <rchapman@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>