vk: Call anv_batch_emit_dwords() up front in anv_batch_emit()
vk: Call anv_batch_emit_dwords() up front in anv_batch_emit()

This avoids putting a memory barrier between the template struct and
the pack function, which generates much better code.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler