nir/builder: Move nir_imm_vec2 from blorp into the builder

While we're here, fix a typo which caused it to actually return a vec4
with the third and fourth components zero.

Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir_builder.h

@@ -279,6 +279,18 @@ nir_imm_floatN_t(nir_builder *build, double x, unsigned bit_size)
    unreachable("unknown float immediate bit size");
 }
 
+static inline nir_ssa_def *
+nir_imm_vec2(nir_builder *build, float x, float y)
+{
+   nir_const_value v;
+
+   memset(&v, 0, sizeof(v));
+   v.f32[0] = x;
+   v.f32[1] = y;
+
+   return nir_build_imm(build, 2, 32, v);
+}
+
 static inline nir_ssa_def *
 nir_imm_vec4(nir_builder *build, float x, float y, float z, float w)
 {