Change in coreboot[master]: sc7180: Add backlight support for sn65dsi86bridge

[Vinod Polimera (Code Review)]

Attention is currently required from: Shelley Chen, Ravi kumar, Julius Werner, mturney mturney.
Vinod Polimera has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52663 )

Change subject: sc7180: Add backlight support for sn65dsi86bridge
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Patch Set 4:

(2 comments)

File src/drivers/ti/sn65dsi86bridge/sn65dsi86bridge.c:

https://review.coreboot.org/c/coreboot/+/52663/comment/a2421419_dd9e754e 
PS1, Line 446: 	sn65dsi86_bridge_dpcd_request(bus, chip, DP_BACKLIGHT_MODE_SET, 1, DPCD_READ, &val);
> Any reason these all need to be read-modify-write? All the other bits are power-on 0 and I don't see […]

Done

https://review.coreboot.org/c/coreboot/+/52663/comment/2fa0299c_42af6652 
PS1, Line 458: 2
> While I'm sure it works that way, the whole "write two bytes because we know the LSB register comes  […]

Done