msm: ipa: add support for QoS Enable IOCTL

Add the RMNET_IOCTL_SET_QOS_ENABLE support to the WWAN driver.
RMNET_IOCTL_SET_QOS_ENABLE returns an error indication to inform that
QoS header addition is not supported.
RMNET_IOCTL_SET_QOS_DISABLE returns success to support Netmgr old code.

Change-Id: I861c2944131a88982a06db20666ae79b4737d81d
Signed-off-by: Ravit Katzav <rkatzav@codeaurora.org>