backend: API to support full precision matmul

Most tensor backends try to optimize performance by using a lower
precision for matmuls. However, some operations (such as kq) on
some models are sensitive to this and require full precision.

ml/backend/ggml/ggml.go

@@ -421,6 +421,15 @@ func (t *Tensor) Mulmat(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
 	}
 }
 
+func (t *Tensor) MulmatFullPrec(ctx ml.Context, t2 ml.Tensor) ml.Tensor {
+	mul := C.ggml_mul_mat(ctx.(*Context).ctx, t.t, t2.(*Tensor).t)
+	C.ggml_mul_mat_set_prec(mul, C.GGML_PREC_F32)
+
+	return &Tensor{
+		t: mul,
+	}
+}
+
 func (t *Tensor) LayerNorm(ctx ml.Context, w, b ml.Tensor, eps float32) ml.Tensor {
 	tt := (&Tensor{t: C.ggml_norm(ctx.(*Context).ctx, t.t, C.float(eps))}).Mul(ctx, w)
 	if b != nil {