arm, davinci: Add lowlevel_init for SoCs other than DM644X

The low level initialization code in
arch/arm/cpu/arm926ejs/davinci/lowlevel_init.S was written for
DM644X SoCs only. This patch makes the lowlevel_init function in this
file a dummy function for SoCs other than DM644X.

Signed-off-by: Christian Riesch <christian.riesch@omicron.at>
Cc: Tom Rini <trini@ti.com>
Cc: Sergey Kubushyn <ksi@koi8.net>
Acked-by: Heiko Schocher <hs@denx.de>
Tested-by: Heiko Schocher <hs@denx.de>

arch/arm/cpu/arm926ejs/davinci/lowlevel_init.S

@@ -49,6 +49,7 @@
 
 .globl	lowlevel_init
 lowlevel_init:
+#ifdef CONFIG_SOC_DM644X
 
 	/*-------------------------------------------------------*
 	 * Mask all IRQs by setting all bits in the EINT default *
@@ -707,3 +708,6 @@ DDR2_START_ADDR:
 	.word	0x80000000
 DUMMY_VAL:
 	.word	0xa55aa55a
+#else /* CONFIG_SOC_DM644X */
+	mov pc, lr
+#endif