test/cmd/mem_copy.c: Use CONFIG_SYS_LOAD_ADDR for base

When reading/writing to memory we cannot assume that a base address of
0x0 is correct and functional. So use CONFIG_SYS_LOAD_ADDR as the base
from which we add a bit more padding and being our tests.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/test/cmd/mem_copy.c b/test/cmd/mem_copy.c
index 1ba0ceb..67eca32 100644
--- a/test/cmd/mem_copy.c
+++ b/test/cmd/mem_copy.c
@@ -21,7 +21,7 @@
 static int do_test(struct unit_test_state *uts,
 		   const char *suffix, int d, int s, int count)
 {
-	const long addr = 0x1000;
+	const long addr = CONFIG_SYS_LOAD_ADDR + 0x1000;
 	u8 shadow[BUF_SIZE];
 	u8 *buf;
 	int i, w, bytes;