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/p2041rdb/Kconfig b/board/freescale/p2041rdb/Kconfig
index 78e1121..7e187dd 100644
--- a/board/freescale/p2041rdb/Kconfig
+++ b/board/freescale/p2041rdb/Kconfig
@@ -9,4 +9,6 @@
 config SYS_CONFIG_NAME
 	default "P2041RDB"
 
+source "board/freescale/common/Kconfig"
+
 endif