fbdev: au1100fb: Fix build on MIPS64

Fix an error reported by the kernel test robot:
au1100fb.c: error: implicit declaration of function 'KSEG1ADDR'; did you mean 'CKSEG1ADDR'?

arch/mips/include/asm/addrspace.h defines KSEG1ADDR only for 32 bit
configurations. So provide its compile-test stub also for 64bit mips builds.

Fixes: 6f366e86481a ("fbdev: au1100fb: Make driver compilable on non-mips platforms")
Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Signed-off-by: Helge Deller <[e-mail]>
Acked-by: Uwe Kleine-König <[e-mail]>

drivers/video/fbdev/au1100fb.c

···
 #define panel_is_color(panel) (panel->control_base & LCD_CONTROL_PC)
 #define panel_swap_rgb(panel) (panel->control_base & LCD_CONTROL_CCO)
 
-#if defined(CONFIG_COMPILE_TEST) && !defined(CONFIG_MIPS)
-/* This is only defined to be able to compile this driver on non-mips platforms */
+#if defined(CONFIG_COMPILE_TEST) && (!defined(CONFIG_MIPS) || defined(CONFIG_64BIT))
+/*
+ * KSEG1ADDR() is defined in arch/mips/include/asm/addrspace.h
+ * for 32 bit configurations. Provide a stub for compile testing
+ * on other platforms.
+ */
 #define KSEG1ADDR(x) (x)
 #endif