r600: factor out the code to initialise a buffer resource.
r600: factor out the code to initialise a buffer resource.

This takes the code required to initialise a buffer resource
out of the texture buffer code, into it's own function.

This is going to be used for the image support later.

Reviewed-by: Edward O'Callaghan <b035da0d7e151e09fe2005f3a7bc526beb9b3245@folklore1984.net>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler