pmdomain: imx8mp-blk-ctrl: Keep the NOC_HDCP clock enabled

Keep the NOC_HDCP clock always enabled to fix the potential hang
caused by the NoC ADB400 port power down handshake.

Fixes: 77b0ddb42add ("soc: imx: add i.MX8MP HDMI blk ctrl HDCP/HRV_MWR")
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>