fbdev/omapfb: 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/omap2/omapfb/Kconfig

···
 	depends on GPIOLIB
 	select FB_OMAP2_DSS
 	select OMAP2_VRFB if ARCH_OMAP2 || ARCH_OMAP3
-	select FB_CFB_FILLRECT
-	select FB_CFB_COPYAREA
-	select FB_CFB_IMAGEBLIT
+	select FB_IOMEM_HELPERS
 	help
 	  Frame buffer driver for OMAP2+ based boards.
 

drivers/video/fbdev/omap2/omapfb/omapfb-main.c

···
 	.owner          = THIS_MODULE,
 	.fb_open        = omapfb_open,
 	.fb_release     = omapfb_release,
-	.fb_fillrect    = cfb_fillrect,
-	.fb_copyarea    = cfb_copyarea,
-	.fb_imageblit   = cfb_imageblit,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
 	.fb_blank       = omapfb_blank,
+	__FB_DEFAULT_IOMEM_OPS_DRAW,
 	.fb_ioctl       = omapfb_ioctl,
 	.fb_check_var   = omapfb_check_var,
 	.fb_set_par     = omapfb_set_par,