of/fdt: move memreserve and dtb memory reservations into core

Move the /memreserve/ processing and dtb memory reservations into
early_init_fdt_scan_reserved_mem. This converts arm, arm64, and powerpc
as they are the only users of early_init_fdt_scan_reserved_mem.

memblock_reserve is safe to call on the same region twice, so the
reservation check for the dtb in powerpc 32-bit reservations is safe to
remove.

Signed-off-by: Rob Herring <robh@kernel.org>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
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 4129f74..051be4c 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -492,9 +492,25 @@
  */
 void __init early_init_fdt_scan_reserved_mem(void)
 {
+	int n;
+	u64 base, size;
+
 	if (!initial_boot_params)
 		return;
 
+	/* Reserve the dtb region */
+	early_init_dt_reserve_memory_arch(__pa(initial_boot_params),
+					  fdt_totalsize(initial_boot_params),
+					  0);
+
+	/* Process header /memreserve/ fields */
+	for (n = 0; ; n++) {
+		fdt_get_mem_rsv(initial_boot_params, n, &base, &size);
+		if (!size)
+			break;
+		early_init_dt_reserve_memory_arch(base, size, 0);
+	}
+
 	of_scan_flat_dt(__fdt_scan_reserved_mem, NULL);
 	fdt_init_reserved_mem();
 }