ac/nir: add always_vector argument to ac_build_gather_values_extended

This simplifies a bunch of places that no longer need special treatment
of value_count == 1. We rely on LLVM to optimize away the 1-element vector
types.

This fixes a bunch of bugs where 1-element arrays are indexed indirectly.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/amd/common/ac_llvm_build.h

@@ -78,7 +78,8 @@ ac_build_gather_values_extended(struct ac_llvm_context *ctx,
 				LLVMValueRef *values,
 				unsigned value_count,
 				unsigned value_stride,
-				bool load);
+				bool load,
+				bool always_vector);
 LLVMValueRef
 ac_build_gather_values(struct ac_llvm_context *ctx,
 		       LLVMValueRef *values,