[RFC PATCH] xtensa: setup: use CONFIG_USE_OF instead of CONFIG_OF

[Randy Dunlap <rdunlap@infradead.org>]

CONFIG_OF can be set by a randconfig or by a user -- without setting the
early flattree option (OF_EARLY_FLATTREE).  This causes build errors.
However, if randconfig or a user sets USE_OF in the Xtensa config,
the right kconfig symbols are set to enable xtensa/kernel/setup.c to
build.

Fixes these build errors:

../arch/xtensa/kernel/setup.c: In function 'xtensa_dt_io_area':
../arch/xtensa/kernel/setup.c:201:14: error: implicit declaration of function 'of_flat_dt_is_compatible'; did you mean 'of_machine_is_compatible'? [-Werror=implicit-function-declaration]
  201 |         if (!of_flat_dt_is_compatible(node, "simple-bus"))
../arch/xtensa/kernel/setup.c:204:18: error: implicit declaration of function 'of_get_flat_dt_prop' [-Werror=implicit-function-declaration]
  204 |         ranges = of_get_flat_dt_prop(node, "ranges", &len);
../arch/xtensa/kernel/setup.c:204:16: error: assignment to 'const __be32 *' {aka 'const unsigned int *'} from 'int' makes pointer from integer without a cast [-Werror=int-conversion]
  204 |         ranges = of_get_flat_dt_prop(node, "ranges", &len);
      |                ^
../arch/xtensa/kernel/setup.c: In function 'early_init_devtree':
../arch/xtensa/kernel/setup.c:228:9: error: implicit declaration of function 'early_init_dt_scan'; did you mean 'early_init_devtree'? [-Werror=implicit-function-declaration]
  228 |         early_init_dt_scan(params);
../arch/xtensa/kernel/setup.c:229:9: error: implicit declaration of function 'of_scan_flat_dt' [-Werror=implicit-function-declaration]
  229 |         of_scan_flat_dt(xtensa_dt_io_area, NULL);

Fixes: da844a81779e ("xtensa: add device trees support")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: linux-xtensa@linux-xtensa.org
---
 arch/xtensa/kernel/setup.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- linux-next-20210917.orig/arch/xtensa/kernel/setup.c
+++ linux-next-20210917/arch/xtensa/kernel/setup.c
@@ -183,7 +183,7 @@ static int __init parse_bootparam(const
 }
 #endif
 
-#ifdef CONFIG_OF
+#ifdef CONFIG_USE_OF
 
 #if !XCHAL_HAVE_PTP_MMU || XCHAL_HAVE_SPANNING_WAY
 unsigned long xtensa_kio_paddr = XCHAL_KIO_DEFAULT_PADDR;
@@ -232,7 +232,7 @@ void __init early_init_devtree(void *par
 		strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
 }
 
-#endif /* CONFIG_OF */
+#endif /* CONFIG_USE_OF */
 
 /*
  * Initialize architecture. (Early stage)
@@ -253,7 +253,7 @@ void __init init_arch(bp_tag_t *bp_start
 	if (bp_start)
 		parse_bootparam(bp_start);
 
-#ifdef CONFIG_OF
+#ifdef CONFIG_USE_OF
 	early_init_devtree(dtb_start);
 #endif