arm64: dts: ti: k3-am65-main: Use lower case hexadecimal

Device tree convention uses lower case a-f for hexadecimals. Fix the
same.

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Acked-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20200903130015.21361-3-nm@ti.com