FIX: "inline" -> "static inline" for bytesFromNibbles and packNibbles

[hoangmit]

Without "static" quantifier, it fails to compile in clang

ld.lld: error: undefined symbol: packNibbles
>>> referenced by ggml.c:520 (llama_cpp/ggml.c:520)
>>>               .../llama_cpp/__ggml__/__objects__/ggml.c.pic.o:(quantize_row_q4_0)

ld.lld: error: undefined symbol: bytesFromNibbles
>>> referenced by ggml.c:1434 (llama_cpp/ggml.c:1434)
>>>               .../llama_cpp/__ggml__/__objects__/ggml.c.pic.o:(ggml_vec_dot_q4_0)
>>> referenced by ggml.c:1435 (llama_cpp/ggml.c:1435)
>>>               .../llama_cpp/__ggml__/__objects__/ggml.c.pic.o:(ggml_vec_dot_q4_0)
clang-12: error: linker command failed with exit code 1 (use -v to see invocation)