FIT: Modify option FIT_SIGNATURE in Kconfig

For FIT signature based approach to work, RSA library needs to be selected.
The FIT_SIGNATURE option in Kconfig is modified to automatically select RSA.
Selecting RSA compiles the RSA library required for image verification.
Signed-off-by: NRuchika Gupta <ruchika.gupta@freescale.com>
CC: Simon Glass <sjg@chromium.org>
Acked-by: NSimon Glass <sjg@chromium.org>

Kconfig

@@ -116,8 +116,9 @@ config FIT_VERBOSE
 	depends on FIT
 
 config FIT_SIGNATURE
-	bool "Enabel signature verification of FIT uImages"
+	bool "Enable signature verification of FIT uImages"
 	depends on FIT
+	select RSA
 	help
 	  This option enables signature verification of FIT uImages,
 	  using a hash signed and verified using RSA.

lib/Kconfig

@@ -27,4 +27,11 @@ config SYS_HZ
 	  get_timer() must operate in milliseconds and this option must be
 	  set to 1000.
 
+config RSA
+	bool "Use RSA Library"
+	help
+	  RSA support. This enables the RSA algorithm used for FIT image
+	  verification in U-Boot.
+	  See doc/uImage.FIT/signature.txt for more details.
+
 endmenu