Clamp the fbdev surface size of the available maximumi height to avoid
failing to init console emulation. An example error is shown below.

  bad framebuffer height 2304, should be >= 768 && <= 768
  [drm] Initialized simpledrm 1.0.0 20200625 for simple-framebuffer.0 on minor 0
  simple-framebuffer simple-framebuffer.0: [drm] *ERROR* fbdev: Failed to setup generic emulation (ret=-22)

This is especially a problem with drivers that have very small screen
sizes and cannot over-allocate at all.

v2:
	* reduce warning level (Ville)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 11e8f5fd ("drm: Add simpledrm driver")
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reported-by: Amanoel Dawod <kernel@amanoeldawod.com>
Reported-by: Zoltán Kővágó <dirty.ice.hu@gmail.com>
Reported-by: Michael Stapelberg <michael+lkml@stapelberg.ch>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.14+
Link: https://patchwork.freedesktop.org/patch/msgid/20211005070355.7680-1-tzimmermann@suse.deSigned-off-by: Dave Airlie <airlied@redhat.com>