ARM: dts: at91: sama5d4: fix instance id of DBGU

Change instance id of DBGU to 45.

Signed-off-by: Mohamed Jamsheeth Hajanajubudeen <mohamedjamsheeth.hajanajubudeen@atmel.com>
Fixes: 7c661394

 ("ARM: at91: dt: add device tree file for SAMA5D4 SoC")
Cc: stable@vger.kernel.org   # 3.18+
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>