i965: Rename brw_compile to brw_codegen

i965: Rename brw_compile to brw_codegen

This name better matches what it's actually used for.  The patch was
generated with the following command:

for file in *; do
sed -i -e s/brw_compile/brw_codegen/g $file
done

Signed-off-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>