configs: Move CONFIG_FIT_SIGNATURE to defconfig

For the platforms which use,CONFIG_FIT_SIGNATURE, the required configs are
moved to the platform's defconfig file. Selecting CONFIG_FIT_SIGNATURE using
defconfig automatically resolves the dependencies for signature verification.
The RSA library gets automatically selected and user does not have to define
CONFIG_RSA manually.

Signed-off-by: Ruchika Gupta <ruchika.gupta@freescale.com>
CC: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/ids8313_defconfig b/configs/ids8313_defconfig
index 1c665aa..8479cd4 100644
--- a/configs/ids8313_defconfig
+++ b/configs/ids8313_defconfig
@@ -1,4 +1,6 @@
 CONFIG_SYS_EXTRA_OPTIONS="SYS_TEXT_BASE=0xFFF00000"
 CONFIG_PPC=y
 CONFIG_MPC83xx=y
+CONFIG_FIT=y
+CONFIG_FIT_SIGNATURE=y
 CONFIG_TARGET_IDS8313=y