boards: arm: Fix sensor shell sample for beagleconnect_freedom board

Commit 944ced68 enabled
CONFIG_UART_CONSOLE=y for the beagleconnect_freedom board, which had the
side effect of satisfying a required dependency for the sensor shell
sample application and causing new build errors in the weekly full
twister run. Fix the build errors by moving the board's light and
humidity sensor nodes to be children of the I2C controller node.

Signed-off-by: Maureen Helm <maureen.helm@analog.com>