Add an interface to determine whether the display supports adjusting the brightness

[wubw0508]

I have three monitors:
1.sudo ddcutil getvcp is supported, and the sudo ddcutil setvcp setting is successful;
2.sudo ddcutil getvcp is supported, but the sudo ddcutil setvcp setting fails.
3.sudo ddcutil getvcp is not supported
If it is the second case, none of the existing methods can effectively determine whether the current display supports ddcutil brightness adjustment.

Through project practice, only by using sudo ddcutil setvcp and then sudo ddcutil getvcp, if it can be set in, it indicates that the display can support brightness adjustment.
Now, add the api interface for this judgment method: ddca_check_brightness_support

Submit link: #537