Support I4 weights pack/unpack.

Signed-off-by: Kevin Cheng <kevin.cheng@arm.com>
Change-Id: Ia7d2bfaa473c8a92c71f075c86aca0a275245f83
diff --git a/include/tosa_serialization_handler.h b/include/tosa_serialization_handler.h
index db9481b..73254dd 100644
--- a/include/tosa_serialization_handler.h
+++ b/include/tosa_serialization_handler.h
@@ -291,6 +291,7 @@
     static tosa_err_t ConvertI32toU8(const std::vector<int32_t>& in, std::vector<uint8_t>& out);
     static tosa_err_t ConvertI16toU8(const std::vector<int16_t>& in, std::vector<uint8_t>& out);
     static tosa_err_t ConvertI8toU8(const std::vector<int8_t>& in, std::vector<uint8_t>& out);
+    static tosa_err_t ConvertI4toU8(const std::vector<int8_t>& in, std::vector<uint8_t>& out);
     static tosa_err_t ConvertBooltoU8(const std::vector<bool>& in, std::vector<uint8_t>& out);
 
     static tosa_err_t ConvertU8toF32(const std::vector<uint8_t>& in, uint32_t out_size, std::vector<float>& out);
@@ -298,6 +299,7 @@
     static tosa_err_t ConvertU8toI32(const std::vector<uint8_t>& in, uint32_t out_size, std::vector<int32_t>& out);
     static tosa_err_t ConvertU8toI16(const std::vector<uint8_t>& in, uint32_t out_size, std::vector<int16_t>& out);
     static tosa_err_t ConvertU8toI8(const std::vector<uint8_t>& in, uint32_t out_size, std::vector<int8_t>& out);
+    static tosa_err_t ConvertU8toI4(const std::vector<uint8_t>& in, uint32_t out_size, std::vector<int8_t>& out);
     static tosa_err_t ConvertU8toBool(const std::vector<uint8_t>& in, uint32_t out_size, std::vector<bool>& out);
 
     // version