[PATCH] drm/mediatek: Fix unused-but-set variable warning

[miles.chen at mediatek.com]

>You are right, in both cases the bit is set, but the funciton does not do what 
>it is supposed to do.
>Will just clear all bits of the mask.
>
>Without your patch, we will just write the val to the register and don't care 
>what the register value was before that.
>
>We should somehow mention that in the commit message, as it's not only about a 
>not used variable, it actually has an influence on the value we write(-back) to 
>the register.

thanks for the comment. I understand that it's not only about a not used
variable. I talked to our hdmi experts and they think mtk_cec_mask() should
write tmp instead of write val to the register.

I will mention this in the commit message and submit next patch.

Happy new year!

Miles