NXP: Introduce board/freescale/common/Kconfig and migrate CHAIN_OF_TRUST

Introduce board/freescale/common/Kconfig so that we have a single place
for CONFIG options that are shared between ARM and PowerPC NXP platforms.

Cc: York Sun <york.sun@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/board/freescale/common/Kconfig b/board/freescale/common/Kconfig
new file mode 100644
index 0000000..38babd3
--- /dev/null
+++ b/board/freescale/common/Kconfig
@@ -0,0 +1,4 @@
+config CHAIN_OF_TRUST
+	depends on !FIT_SIGNATURE && SECURE_BOOT
+	bool
+	default y