net: ipa: modem: add missing SET_NETDEV_DEV() for proper sysfs links

At the moment it is quite hard to identify the network interface
provided by IPA in userspace components: The network interface is
created as virtual device, without any link to the IPA device.
The interface name ("rmnet_ipa%d") is the only indication that the
network interface belongs to IPA, but this is not very reliable.

Add SET_NETDEV_DEV() to associate the network interface with the
IPA parent device. This allows userspace services like ModemManager
to properly identify that this network interface is provided by IPA
and belongs to the modem.

Cc: Alex Elder <elder@kernel.org>
Fixes: a646d6ec

 ("soc: qcom: ipa: modem and microcontroller")
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20210106100755.56800-1-stephan@gerhold.net


Signed-off-by: Jakub Kicinski <kuba@kernel.org>