ARM: dts: at91: sama5d2: add ETB and ETM unit name

Add unit address to the ETB and ETM nodes.

It also allow us to get rid of the warnings:
../arch/arm/boot/dts/sama5d2.dtsi:43.6-57.4: Warning
(unit_address_vs_reg): /etb: node has a reg or ranges property, but no
unit name
../arch/arm/boot/dts/sama5d2.dtsi:59.6-73.4: Warning
(unit_address_vs_reg): /etm: node has a reg or ranges property, but no
unit name
when we compile with W=1.

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210402170139.140595-1-nicolas.ferre@microchip.com