net: ipa: inter-EE interrupts aren't always available

The GSI inter-EE interrupts are not supported prior to IPA v3.5.
Don't attempt to initialize them in gsi_irq_setup() for hardware
that does not support them.

Originally proposed by AngeloGioacchino Del Regno.

Link: https://lore.kernel.org/netdev/20210211175015.200772-4-angelogioacchino.delregno@somainline.org


Signed-off-by: Alex Elder <elder@linaro.org>
Acked-by: AngeloGioacchino Del Regno
Signed-off-by: David S. Miller <davem@davemloft.net>