va: Fix 4:2:2 jpeg decoding
- enhance the jpeg decoder template caps by removing those subsamplings without reported pixel formats (useful for mesa gallium)
- add y42b color format for 4:2:2
- handle 4:2:2 for i965 with nv12 (by using its internal color conversion)
- fixed a potential critical message when a non-valid caps configuration is reached.
- fixed a couple mem leaks.
Fixes: #1378 (closed)
Edited by Víctor Manuel Jáquez Leal