dt-bindings: soc: imx-blk-ctrl: Drop leading label in blk-ctrl in examples

Drop the leading label in block controller examples, it is unused.

Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>