ARM: at91/config: sama5: Remove DEBUG_LL

The sama5_defconfig can be used both on the sama5d3 and the sama5d4.

Enabling DEBUG_LL is an issue though, since it will by default use the kernel
addresses for the sama5d3 DBGU UART, that is located at a different address on
the sama5d4.

Remove this from the defconfig.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>