uio_netx: Compiling the kernel module may emit a lot of warnings about twice exported symbols

Due to updates of the kernel build environment, the current Makefile call of the modpost step leads to a second export of the symbols.

Warnings may look like:

WARNING: modpost: arch/x86/kvm/kvm: '__tracepoint_kvm_entry' exported twice. Previous export was in arch/x86/kvm/kvm.ko