powerpc/boot: Only free if realloc() succeeds

simple_realloc() frees the original buffer (ptr) even if the
reallocation failed.

Fix it to behave like standard realloc() and only free the original
buffer if the reallocation succeeded.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240229115149.749264-1-mpe@ellerman.id.au

arch/powerpc/boot/simple_alloc.c

@@ -112,10 +112,11 @@ static void *simple_realloc(void *ptr, unsigned long size)
 		return ptr;
 
 	new = simple_malloc(size);
-	if (new)
+	if (new) {
 		memcpy(new, ptr, p->size);
-
 		simple_free(ptr);
+	}
+
 	return new;
 }