multimedia/libva-intel-driver: clean up descriptions
- Spell Intel properly as the driver is named i965
- Mention support for Gen4/Gen5
- Disambiguate COMMENT from libva-intel-media-driver
- Simplify ONLY_FOR_ARCHS_REASON wording
- Move ONLY_FOR_ARCHS to pacify portlint -C
- Mention HYBRID support for VP8 encoding
- Update WWW to actual homepage
- Expand pkg-descr with from upstream README.md
Approved by: madpilot (maintainer)
Differential Revision: https://reviews.freebsd.org/D18688