The CTA-861 standards have been updated to refer to opRGB instead

The CTA-861 standards have been updated to refer to opRGB instead
of AdobeRGB. The official standard is in fact named opRGB, so
switch to that.

The two old defines referring to ADOBERGB in the public API are
put under #ifndef _KERNEL and a comment mentions that they are
deprecated.

This keeps us in sync with the linux header.

ok feinerer@, mpi@, deraadt@