simplefb: add goto error path to probe

Use the usual kernel style of goto error_foo to free resources on probe
error. This is a preparation patch for adding clocks support.

While at it also update ioremap_wc error return from ENODEV to ENOMEM.

Signed-off-by: Luc Verhaegen <libv@skynet.be>
Acked-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>