vgacon: clean up global screen_info instances

To prepare for completely separating the VGA console screen_info from
the one used in EFI/sysfb, rename the vgacon instances and make them
local as much as possible.

ia64 and arm both have confurations with vgacon and efi, but the contents
never overlaps because ia64 has no EFI framebuffer, and arm only has
vga console on legacy platforms without EFI. Renaming these is required
before the EFI screen_info can be moved into drivers/firmware.

The ia64 vga console is actually registered in two places from
setup_arch(), but one of them is wrong, so drop the one in pcdp.c and
fix the one in setup.c to use the correct conditional.

x86 has to keep them together, as the boot protocol is used to switch
between VGA text console and framebuffer through the screen_info data.

Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Khalid Aziz <khalid@gonehiking.org>
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20231009211845.3136536-7-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/alpha/kernel/setup.c

@@ -138,7 +138,7 @@ static char __initdata command_line[COMMAND_LINE_SIZE];
  * code think we're on a VGA color display.
  */
 
-struct screen_info screen_info = {
+struct screen_info vgacon_screen_info = {
 	.orig_x = 0,
 	.orig_y = 25,
 	.orig_video_cols = 80,
@@ -146,8 +146,6 @@ struct screen_info screen_info = {
 	.orig_video_isVGA = 1,
 	.orig_video_points = 16
 };
-
-EXPORT_SYMBOL(screen_info);
 #endif
 
 /*
@@ -654,7 +652,7 @@ setup_arch(char **cmdline_p)
 
 #ifdef CONFIG_VT
 #if defined(CONFIG_VGA_CONSOLE)
-	vgacon_register_screen(&screen_info);
+	vgacon_register_screen(&vgacon_screen_info);
 #endif
 #endif