msm ipa: fix set_qos_enable ioctl in wan-driver

in LA, user-space module will try to check if qos
is supported via the ioctl, RMNET_IOCTL_SET_QOS_ENABLE,
to wan-transport driver and it should directly return
"-EINVAL".

Change-Id: Ia62d225d0cc9084e9a3754e48e79a8b472a0ddb6
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>