Add scalar version of hwc2spchw convolution.

PiperOrigin-RevId: 276274887
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f356b60..0df9150 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -167,6 +167,7 @@
   src/f32-avgpool/mp9p8q-scalar.c
   src/f32-avgpool/up9-scalar.c
   src/f32-clamp/scalar.c
+  src/f32-conv-hwc2spchw/3x3s2p1c3x4-scalar-1x1.c
   src/f32-igemm/1x4-scalar.c
   src/f32-igemm/2x4-scalar.c
   src/f32-igemm/4x2-scalar.c