samples: bluetooth: mesh: dfu: distributor: Enable RTT explicitly

This option is not enabled by default and apparently not enabled through
some other Kconfig options on nRF54L15. Enabling it explicitly to avoid
misconfiguration of the sample.

Signed-off-by: Pavel Vasilyev <[email protected]>
(cherry picked from commit ecc960b)

Author: PavelVPV

samples/bluetooth/mesh/dfu/distributor/prj.conf

@@ -103,3 +103,7 @@ CONFIG_SEGGER_RTT_BUFFER_SIZE_DOWN=100
 # MCUmgr UART transport
 CONFIG_BASE64=y
 CONFIG_MCUMGR_TRANSPORT_UART=y
+
+# This option may not be enabled automatically for some boards. Enabling it explicitly to avoid
+# missing configuration.
+CONFIG_USE_SEGGER_RTT=y