Move CONFIG_PANIC_HANG to Kconfig

Freescale (NXP) boards have lots of defconfig files per board.
I used "imply PANIC_HANG" for them.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/configs/TWR-P1025_defconfig b/configs/TWR-P1025_defconfig
index 1eedd3c..1eeb590 100644
--- a/configs/TWR-P1025_defconfig
+++ b/configs/TWR-P1025_defconfig
@@ -35,4 +35,5 @@
 CONFIG_FSL_ESPI=y
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y
+CONFIG_PANIC_HANG=y
 CONFIG_OF_LIBFDT=y