[PATCH] video: fbdev: controlfb: fix build for COMPILE_TEST=y && PPC_PMAC=y && PPC32=n

powerpc allyesconfig fails like this:

drivers/video/fbdev/controlfb.c: In function 'controlfb_mmap':
drivers/video/fbdev/controlfb.c:756:23: error: implicit declaration of function 'pgprot_cached_wthru'; did you mean 'pgprot_cached'? [-Werror=implicit-function-declaration]
  756 |   vma->vm_page_prot = pgprot_cached_wthru(vma->vm_page_prot);
      |                       ^~~~~~~~~~~~~~~~~~~
      |                       pgprot_cached
drivers/video/fbdev/controlfb.c:756:23: error: incompatible types when assigning to type 'pgprot_t' {aka 'struct <anonymous>'} from type 'int'

Fix it by adding missing PPC32 dependency.

Fixes: a07a63b0e24d ("video: fbdev: controlfb: add COMPILE_TEST support")
Reported-by: Stephen Rothwell <redacted>
Reported-by: kbuild test robot <redacted>
Cc: Sam Ravnborg <redacted>
Cc: Daniel Vetter <redacted>
Signed-off-by: Bartlomiej Zolnierkiewicz <redacted>
---
 drivers/video/fbdev/controlfb.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: b/drivers/video/fbdev/controlfb.c
=================================--- a/drivers/video/fbdev/controlfb.c

+++ b/drivers/video/fbdev/controlfb.c

@@ -47,7 +47,7 @@
 #include <linux/nvram.h>
 #include <linux/adb.h>
 #include <linux/cuda.h>
-#ifdef CONFIG_PPC_PMAC
+#if defined(CONFIG_PPC_PMAC) && defined(CONFIG_PPC32)
 #include <asm/prom.h>
 #include <asm/btext.h>
 #endif

@@ -55,7 +55,7 @@
 #include "macmodes.h"
 #include "controlfb.h"
 
-#ifndef CONFIG_PPC_PMAC
+#if !defined(CONFIG_PPC_PMAC) || !defined(CONFIG_PPC32)
 #define invalid_vram_cache(addr)
 #undef in_8
 #undef out_8