drm/rockchip: vop2: Check bpc before switching DCLK source

drm/rockchip: vop2: Check bpc before switching DCLK source

When making use of the HDMI PHY PLL as a VOP2 DCLK source, it's output
rate does normally match the mode clock.  But this is only applicable
for default color depth of 8 bpc.  For higher depths, the output clock
is further divided by the hardware according to the formula:

  output rate = PHY PLL rate * 8 / bpc

Hence there is no need for VOP2 to compensate for bpc when adjusting
DCLK, but it is required to do so when computing its maximum operating
frequency.

Take color depth into consideration before deciding to switch DCLK
source.

Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20251021-rk3588-10bpc-v3-1-3d3eed00a6db@collabora.com