powerpc/boot: Allocate more memory for dtb

David Gibson suggested that since we are now unconditionally copying
the dtb into a malloc()ed buffer, it would be sensible to add a little
padding to the buffer at that point, so that further device tree
manipulations won't need to reallocate it.

This implements that suggestion.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/boot/libfdt-wrapper.c

@@ -185,7 +185,7 @@ void fdt_init(void *blob)
 
 	/* Make sure the dt blob is the right version and so forth */
 	fdt = blob;
-	bufsize = fdt_totalsize(fdt) + 4;
+	bufsize = fdt_totalsize(fdt) + EXPAND_GRANULARITY;
 	buf = malloc(bufsize);
 	if(!buf)
 		fatal("malloc failed. can't relocate the device tree\n\r");