Revert "of/fdt: Make sure no-map does not remove already reserved regions"

This reverts commit 666ae7c255.
It is not really a fix, and the backport misses dependencies, which
breaks existing platforms.

Reported-by: Alexandre TORGUE <alexandre.torgue@foss.st.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/of/fdt.c

@@ -1192,16 +1192,8 @@ void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
 int __init __weak early_init_dt_reserve_memory_arch(phys_addr_t base,
 					phys_addr_t size, bool nomap)
 {
-	if (nomap) {
-		/*
-		 * If the memory is already reserved (by another region), we
-		 * should not allow it to be marked nomap.
-		 */
-		if (memblock_is_region_reserved(base, size))
-			return -EBUSY;
-
+	if (nomap)
 		return memblock_mark_nomap(base, size);
-	}
 	return memblock_reserve(base, size);
 }