armv7: ls1021a: Move SECURE_BOOT option to Kconfig

Move from CONFIG_SYS_EXTRA_OPTIONS to Kconfig option.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/arm/cpu/armv7/ls102xa/Kconfig b/arch/arm/cpu/armv7/ls102xa/Kconfig
index 28bf778..f94568a 100644
--- a/arch/arm/cpu/armv7/ls102xa/Kconfig
+++ b/arch/arm/cpu/armv7/ls102xa/Kconfig
@@ -28,6 +28,12 @@
 	int "Maximum DDR controllers"
 	default 1
 
+config SECURE_BOOT
+	bool	"Secure Boot"
+	help
+		Enable Freescale Secure Boot feature. Normally selected
+		by defconfig. If unsure, do not change.
+
 config SYS_FSL_ERRATUM_A010315
 	bool "Workaround for PCIe erratum A010315"