i965: Rename INTEL_DEBUG=vec4vs to INTEL_DEBUG=vec4.

i965: Rename INTEL_DEBUG=vec4vs to INTEL_DEBUG=vec4.

driParseDebugString() doesn't have actual code to parse comma separated
lists (or any other supported options?); instead it dumbly uses strstr().

This means that INTEL_DEBUG="vec4vs" will trigger both DEBUG_VEC4VS and
DEBUG_VS, as "vs" is also a substring.

We should probably improve the driconf parsing, but for now, just rename
the option so it's usable in the meantime.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Jason Ekstrand <jason.ekstrand@intel.com>
Acked-by: Kristian Høgsberg <krh@bitplanet.net>