i965/vec4: Use NIR remapping for VS attributes

The NIR pass already handles remapping system values to attributes for
us so we delete the system value code as part of the conversion.

We also change nir_lower_vs_inputs to take an explicit inputs_read
bitmask and pass in the inputs_read from prog_data instead from pulling
it out of NIR.  This is because the version in prog_data may get
EDGEFLAG added to it on some old platforms.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/intel/compiler/brw_nir.c

@@ -230,7 +230,6 @@ remap_patch_urb_offsets(nir_block *block, nir_builder *b,
 
 void
 brw_nir_lower_vs_inputs(nir_shader *nir,
-                        bool is_scalar,
                         bool use_legacy_snorm_formula,
                         const uint8_t *vs_attrib_wa_flags)
 {
@@ -253,11 +252,7 @@ brw_nir_lower_vs_inputs(nir_shader *nir,
    brw_nir_apply_attribute_workarounds(nir, use_legacy_snorm_formula,
                                        vs_attrib_wa_flags);
 
-   /* The last step is to remap VERT_ATTRIB_* to actual registers and we only
-    * do that for scalar shaders at the moment.
-    */
-   if (!is_scalar)
-      return;
+   /* The last step is to remap VERT_ATTRIB_* to actual registers */
 
    /* Whether or not we have any system generated values.  gl_DrawID is not
     * included here as it lives in its own vec4.