Sketch a B-H hysteresis curve of permanent magnet

There's no way from that information to infer the hysteresis curve. Let me explain why.

In general, in a magnetized material, the relationship between magnetic flux density, magnetic field and magnetization is given by (SI units):

$$boldsymbol{B} = mu_0(boldsymbol{H}+boldsymbol{M})$$

The two relationships that you have written in your question represent exactly that relationship. To draw the hysteresis curve, you would need the additional relationship between $boldsymbol{M}$ and $boldsymbol{H}$, and this is missing.

Note also that by assuming a uniform magnetization you get an $boldsymbol{H}$ field which depends on $z$, and which is actually opposite to the magnetization. This is called the demagnetizing field. Its dependence on $z$ is caused by the boundary conditions that $boldsymbol{B}$ and $boldsymbol{H}$ should satisfy at the cylinder's surface. In a real magnet, since $boldsymbol{M}$ depends on $boldsymbol{H}$, the magnetization would also depend on $z$. This means that a cylinder cannot support a uniform magnetization. In fact, the ellipsoid is the only known shape that can support a uniform magnetization [1].

So, you can just draw a generic hysteresis curve.

[1] Some sources seem to imply that this is the only shape with this property. The main reference for this seems to be J. A. Osborn , "Demagnetizing Factors of the General Ellipsoid", Phys. Rev., vol. 67, pp. 351-357, 1945. Here the author says (bold mine):

However, for homogeneous bodies whose surface is of second degree,¹ $H$ and $J$ (after suitable magnetic treatment)) are uniform throughout [...] The ellipsoid has the only surface of the second degree that is finite [...]

Reference¹ is from Maxwell nonetheless: J. C. Maxwell, Electricity and Magnetism, vol. 2, pp. 66-70, The Clarendon Press, 3rd ed., 1904. Here Maxwell proves that (thanks to hyportnex for digging the result) the (magnetic) potential $V$ must be a quadratic function of the position to have a uniform field inside and then he writes

"Now the only cases with which we are acquainted in which V is a quadratic function of the coordinates within the body are those in which the body is bounded by a complete surface of the second degree, and the only case in which such a body is of finite dimensions is when it is an ellipsoid. We shall therefore apply the method to the case of an ellipsoid.