* ggml: uniformize im2col dst_type for all conv ops * Update ggml/src/ggml.c Co-authored-by: Georgi Gerganov <ggerganov@gmail.com> * ggml : uniformize im2col casting logic across all conv ops * fix : allow im2col_f16 to accept any kernel type --------- Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>