nir: Drop the vs_inputs_dual_locations option

It was very inconsistently handled; the only things that made use of it
were glsl_to_nir, glspirv, and nir_gather_info.  In particular,
nir_lower_io completely ignored it so anyone using nir_lower_io on
64-bit vertex attributes was going to be in for a shock.  Also, as of
the previous commit, it's set by every driver that supports 64-bit
vertex attributes.  There's no longer any reason to have it be an option
so let's just delete it.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

src/compiler/nir/nir.h

@@ -2119,12 +2119,6 @@ typedef struct nir_shader_compiler_options {
     */
    bool use_interpolated_input_intrinsics;
 
-   /**
-    * Do vertex shader double inputs use two locations? The Vulkan spec
-    * requires two locations to be used, OpenGL allows a single location.
-    */
-   bool vs_inputs_dual_locations;
-
    unsigned max_unroll_iterations;
 } nir_shader_compiler_options;
 
@@ -3039,9 +3033,8 @@ bool nir_opt_conditional_discard(nir_shader *shader);
 
 void nir_sweep(nir_shader *shader);
 
-uint64_t nir_get_dual_slot_attributes(nir_shader *shader);
 void nir_remap_dual_slot_attributes(nir_shader *shader,
-                                    uint64_t dual_slot);
+                                    uint64_t *dual_slot_inputs);
 uint64_t nir_get_single_slot_attribs_mask(uint64_t attribs, uint64_t dual_slot);
 
 nir_intrinsic_op nir_intrinsic_from_system_value(gl_system_value val);