fbdev/sm712fb: 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 <tzimmermann@suse.de>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Teddy Wang <teddy.wang@siliconmotion.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230927074722.6197-38-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -1938,9 +1938,7 @@ config FB_SSD1307
 config FB_SM712
 	tristate "Silicon Motion SM712 framebuffer support"
 	depends on FB && PCI
-	select FB_CFB_FILLRECT
-	select FB_CFB_COPYAREA
-	select FB_CFB_IMAGEBLIT
+	select FB_IOMEM_HELPERS
 	select VIDEO_NOMODESET
 	help
 	  Frame buffer driver for the Silicon Motion SM710, SM712, SM721

drivers/video/fbdev/sm712fb.c

@@ -1347,6 +1347,7 @@ static int smtc_set_par(struct fb_info *info)
 
 static const struct fb_ops smtcfb_ops = {
 	.owner        = THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
 	.fb_check_var = smtc_check_var,
 	.fb_set_par   = smtc_set_par,
 	.fb_setcolreg = smtc_setcolreg,