Generate callback functions for struct fb_ops with the fbdev macro
FB_GEN_DEFAULT_DEFERRED_IOMEM_OPS(). Initialize struct fb_ops to
the generated functions with fbdev initializer macros.

The hyperv_fb driver is incomplete in its handling of deferred I/O
and damage framebuffers. Write operations do no trigger damage handling.
Fixing this is beyond the scope of this patch.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230828132131.29295-5-tzimmermann@suse.de