fbdev/cobalt-lcd: Initialize fb_ops to fbdev I/O-memory helpers

Initialize the instance of struct fb_ops with fbdev initializer
macros for framebuffers in I/O address space. Set the read/write,
draw and mmap callbacks to the correct implementation and avoid
implicit defaults. Also select the necessary I/O helpers in Kconfig.

Fbdev drivers sometimes rely on the callbacks being NULL for a
default implementation to be invoked; hence requiring the I/O
helpers to be built in any case. Setting all callbacks in all
drivers explicitly will allow to make the I/O helpers optional.
This benefits systems that do not use these functions.

No functional changes.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Acked-by: Javier Martinez Canillas <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/video/fbdev/Kconfig

···
 config FB_COBALT
 	tristate "Cobalt server LCD frame buffer support"
 	depends on FB && MIPS_COBALT
+	select FB_IOMEM_HELPERS
 
 config FB_SH7760
 	bool "SH7760/SH7763/SH7720/SH7721 LCDC support"

drivers/video/fbdev/cobalt_lcdfb.c

···
 	.fb_read	= cobalt_lcdfb_read,
 	.fb_write	= cobalt_lcdfb_write,
 	.fb_blank	= cobalt_lcdfb_blank,
+	__FB_DEFAULT_IOMEM_OPS_DRAW,
 	.fb_cursor	= cobalt_lcdfb_cursor,
+	__FB_DEFAULT_IOMEM_OPS_MMAP,
 };
 
 static int cobalt_lcdfb_probe(struct platform_device *dev)