genxml: Fill out Gen4, Gen45 and Gen5 XML

genxml: Fill out Gen4, Gen45 and Gen5 XML

Add some more details to Gen4 and Gen45 and add what is needed
in Gen5 XML. This commit overwrite the previous work done on Gen4
and Gen45 as it contains more instructions and fixes some mistakes.
However, comments (dword boundaries) are lost in the process.

v3:
   - Set the type of some fields, instead of prefix. Also fix the
     SAMPLER_BORDER_COLOR_STATE fields of gen5.xml.

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Acked-by: Kenneth Graunke <kenneth@whitecape.org>