of/flattree: Add Kconfig for EARLY_FLATTREE

The device tree code is now in two pieces: some which can be used generically
on any platform which selects CONFIG_OF_FLATTREE, and some early which is used
at boot time on only a few architectures.  This patch segregates the early
code so that only those architectures which care about it need compile it.
This also means that some of the requirements in the early code (such as
a cmd_line variable) that most architectures (e.g. X86) don't provide
can be ignored.

Signed-off-by: Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>
[grant.likely@secretlab.ca: remove extra blank line addition]
[grant.likely@secretlab.ca: fixed incorrect #ifdef CONFIG_EARLY_FLATTREE check]
[grant.likely@secretlab.ca: Made OF_EARLY_FLATTREE select instead of depend
                            on OF_FLATTREE]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/of/fdt.c

@@ -27,6 +27,8 @@ int __initdata dt_root_size_cells;
 
 struct boot_param_header *initial_boot_params;
 
+#ifdef CONFIG_OF_EARLY_FLATTREE
+
 char *find_flat_dt_string(u32 offset)
 {
 	return ((char *)initial_boot_params) +
@@ -604,3 +606,5 @@ void __init unflatten_device_tree(void)
 
 	pr_debug(" <- unflatten_device_tree()\n");
 }
+
+#endif /* CONFIG_OF_EARLY_FLATTREE */