dt-bindings: net: marvell-pp2: update interrupt-names with TX interrupts

The PPv2.2 unit has several interrupts used for TX completion
notification. This commit updates the Device Tree binding describing
this HW block to mention such interrupts.

While at it, we update the example to use a recent Device Tree
example, that uses interrupts going through the ICU, and not to the
GIC directly.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>