nir: Add nir_alu_srcs_negative_equal

v2: Move bug fix in get_neg_instr from the next patch to this patch
(where it was intended to be in the first place).  Noticed by Caio.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/nir/nir.h

@@ -997,6 +997,10 @@ bool nir_const_value_negative_equal(const nir_const_value *c1,
 bool nir_alu_srcs_equal(const nir_alu_instr *alu1, const nir_alu_instr *alu2,
                         unsigned src1, unsigned src2);
 
+bool nir_alu_srcs_negative_equal(const nir_alu_instr *alu1,
+                                 const nir_alu_instr *alu2,
+                                 unsigned src1, unsigned src2);
+
 typedef enum {
    nir_deref_type_var,
    nir_deref_type_array,