of/fdt: convert initial_boot_params to opaque pointer

Now that all accesses to FDT header data has been converted to accessor
helpers, initial_boot_params can become an opaque pointer.

Signed-off-by: Rob Herring <robh@kernel.org>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Tested-by: Grant Likely <grant.likely@linaro.org>
Tested-by: Stephen Chivers <schivers@csc.com>
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 358bcf0..a6f83ea 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -372,7 +372,7 @@
 int __initdata dt_root_addr_cells;
 int __initdata dt_root_size_cells;
 
-struct boot_param_header *initial_boot_params;
+void *initial_boot_params;
 
 #ifdef CONFIG_OF_EARLY_FLATTREE