of: consolidate definition of early_init_dt_alloc_memory_arch()

Most architectures use the same implementation. Collapse the common ones
into a single weak function that can be overridden.

Signed-off-by: Grant Likely <grant.likely@linaro.org>

arch/microblaze/kernel/prom.c

@@ -46,11 +46,6 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 	memblock_add(base, size);
 }
 
-void * __init early_init_dt_alloc_memory_arch(u64 size, u64 align)
-{
-	return __va(memblock_alloc(size, align));
-}
-
 #ifdef CONFIG_EARLY_PRINTK
 static char *stdout;