MLK-18726-1: hdmi: Disable GCP when bpp is 24 to pass CTS 7-19

MLK-18726-1: hdmi: Disable GCP when bpp is 24 to pass CTS 7-19

Refer to HDMI 1.4 section 6.5.3, non-zero CD data GCP should send in
deep color mode.
Now, when HDMI work in 24bpp, it will send non-zero CD(0x4 for 24bit)
data GCP to protocol analyzer.
It means current HDMI source is working in “24bit deep color mode”.

But HDMI 1.4 CTS 7-19 required DUT should in “No Deep Color support”.
Protocol analyzer expect received zero CD GCP or no GCP.

Disable GCP when bpp is 24 to pass CTS 7-19.

Signed-off-by: Sandor Yu <Sandor.yu@nxp.com>