samples: wifi: ble_coex: Increase BT controller data length to 251

The default controller data length for single-core builds is 27 bytes,
which limits Bluetooth LE throughput. Increasing this value to 251
enables Data Length Extension (DLE) and improves throughput to match
dual-core platforms.

This change is platform-agnostic and works for both single-core and
dual-core builds.

Signed-off-by: Murali Thokala <[email protected]>

Author: muraliThokala

samples/wifi/ble_coex/prj.conf

@@ -119,3 +119,8 @@ CONFIG_NRF70_QSPI_LOW_POWER=n
 CONFIG_NRF_RPC=n
 CONFIG_NRF_RPC_CBOR=n
 CONFIG_MBEDTLS_HEAP_SIZE=1024
+
+# Increase controller data length to 251 for higher BLE throughput.
+# This setting is platform-agnostic and required for single-core builds.
+# For dual-core builds, sysbuild already propagates this Kconfig to the net/radio core.
+CONFIG_BT_CTLR_DATA_LENGTH_MAX=251