fbdev/hgafb: 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: Ferenc Bakonyi <fero@drama.obuda.kando.hu>
Link: https://patchwork.freedesktop.org/patch/msgid/20230927074722.6197-17-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -485,6 +485,7 @@ config FB_N411
 config FB_HGA
 	tristate "Hercules mono graphics support"
 	depends on FB && X86
+	select FB_IOMEM_FOPS
 	help
 	  Say Y here if you have a Hercules mono graphics card.
 

drivers/video/fbdev/hgafb.c

@@ -532,12 +532,14 @@ static const struct fb_ops hgafb_ops = {
 	.owner		= THIS_MODULE,
 	.fb_open	= hgafb_open,
 	.fb_release	= hgafb_release,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
 	.fb_setcolreg	= hgafb_setcolreg,
 	.fb_pan_display	= hgafb_pan_display,
 	.fb_blank	= hgafb_blank,
 	.fb_fillrect	= hgafb_fillrect,
 	.fb_copyarea	= hgafb_copyarea,
 	.fb_imageblit	= hgafb_imageblit,
+	__FB_DEFAULT_IOMEM_OPS_MMAP,
 };
 
 /* ------------------------------------------------------------------------- *