imx6: Add imx6_src_get_boot_mode

For i.MX6, the bootmode determine code is part of spl_boot_device,
but there is might be a possibility for other part the code need to
check the desired boot mode for adding new functionalities like
modeboot env variable, or changing boot order etc.

So introduced imx6_src_get_boot_mode which actually reading the
boot mode register for desired modes.

More cleanup will be add in future patches.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Matteo Lisi <matteo.lisi@engicam.com>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Jagan Teki <jagan@openedev.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/imx-common/init.c b/arch/arm/imx-common/init.c
index e5dbd93..036ebb2 100644
--- a/arch/arm/imx-common/init.c
+++ b/arch/arm/imx-common/init.c
@@ -115,3 +115,15 @@
 	writel(reg, &psrc->gpr10);
 }
 #endif
+
+#if defined(CONFIG_MX6)
+u32 imx6_src_get_boot_mode(void)
+{
+	struct src *psrc = (struct src *)SRC_BASE_ADDR;
+
+	if (imx6_is_bmode_from_gpr9())
+		return readl(&psrc->gpr9);
+	else
+		return readl(&psrc->sbmr1);
+}
+#endif