add 3x3p1_scalar kernel

PiperOrigin-RevId: 274778298
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1097cfb..3b483af 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -174,6 +174,7 @@
   src/f32-dwconv/up1x25-scalar.c
   src/f32-dwconv/up1x4-scalar.c
   src/f32-dwconv/up1x9-scalar.c
+  src/f32-dwconv-spchw/3x3p1-scalar.c
   src/f32-gavgpool/mp7p7q-scalar.c
   src/f32-gavgpool/up7-scalar.c
   src/f32-gemm/1x4-scalar.c