ARM: imx: mark .dt_compat as const

Otherwise GCC will mark the .init.rodata section R/W, which causes
a compile error once we add other real R/O data.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

arch/arm/mach-imx/imx35-dt.c

@@ -34,7 +34,7 @@ static void __init imx35_irq_init(void)
 	mx35_init_irq();
 }
 
-static const char *imx35_dt_board_compat[] __initconst = {
+static const char * const imx35_dt_board_compat[] __initconst = {
 	"fsl,imx35",
 	NULL
 };