mx25: Fix boot hang by avoiding vector relocation

Since commit 3ff46cc42b ("arm: relocate the exception vectors") mx25pdk
hangs like this:

CPU:   Freescale i.MX25 rev1.2 at 399 MHz
Reset cause: WDOG
Board: MX25PDK
I2C:   ready
DRAM:  64 MiB
(hangs)

Add a specific relocate_vectors macro that skips the vector relocation, as the
i.MX25 SoC does not provide RAM at the high vectors address (0xFFFF0000), and
(0x00000000) maps to ROM.

This allows mx25 to boot again.

Acked-By: Bill Pringlemeir <bpringlemeir@nbsps.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

arch/arm/cpu/arm926ejs/mx25/Makefile

@@ -5,3 +5,7 @@
 # SPDX-License-Identifier:	GPL-2.0+
 
 obj-y	= generic.o timer.o reset.o
+
+ifndef CONFIG_SPL_BUILD
+obj-y	+= relocate.o
+endif

arch/arm/cpu/arm926ejs/mx25/relocate.S

@@ -0,0 +1,23 @@
+/*
+ *  relocate - i.MX25-specific vector relocation
+ *
+ *  Copyright (c) 2013  Albert ARIBAUD <albert.u.boot@aribaud.net>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <linux/linkage.h>
+
+/*
+ * The i.MX25 SoC is very specific with respect to exceptions: it
+ * does not provide RAM at the high vectors address (0xFFFF0000),
+ * thus only the low address (0x00000000) is useable; but that is
+ * in ROM, so let's avoid relocating the vectors.
+ */
+	.section	.text.relocate_vectors,"ax",%progbits
+
+ENTRY(relocate_vectors)
+
+	bx	lr
+
+ENDPROC(relocate_vectors)