Build: Add RSA-3072 support

PSA TBSA-M recommends to use RSA signature for firmware
authentication with at least 3072 bits length key size.

Change-Id: I0689123d61b55167b3efab90fe520e94d9586055
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
diff --git a/bl2/ext/mcuboot/CMakeLists.txt b/bl2/ext/mcuboot/CMakeLists.txt
index 06e0d5b..19ddf3d 100644
--- a/bl2/ext/mcuboot/CMakeLists.txt
+++ b/bl2/ext/mcuboot/CMakeLists.txt
@@ -130,12 +130,19 @@
 
 #Set macro definitions for the project.
 target_compile_definitions(${PROJECT_NAME} PRIVATE
-							MCUBOOT_SIGN_RSA
 							MCUBOOT_VALIDATE_SLOT0
 							MCUBOOT_USE_FLASH_AREA_GET_SECTORS
 							MBEDTLS_CONFIG_FILE="config-boot.h"
 							MCUBOOT_TARGET_CONFIG="flash_layout.h")
 
+if (MCUBOOT_SIGNATURE_TYPE STREQUAL "RSA-3072")
+	target_compile_definitions(${PROJECT_NAME} PRIVATE MCUBOOT_SIGN_RSA MCUBOOT_SIGN_RSA_LEN=3072)
+elseif(MCUBOOT_SIGNATURE_TYPE STREQUAL "RSA-2048")
+	target_compile_definitions(${PROJECT_NAME} PRIVATE MCUBOOT_SIGN_RSA MCUBOOT_SIGN_RSA_LEN=2048)
+else()
+	message(FATAL_ERROR "${MCUBOOT_SIGNATURE_TYPE} is not supported as firmware signing algorithm")
+endif()
+
 if (${MCUBOOT_UPGRADE_STRATEGY} STREQUAL "OVERWRITE_ONLY")
 	target_compile_definitions(${PROJECT_NAME} PRIVATE MCUBOOT_OVERWRITE_ONLY)
 elseif (${MCUBOOT_UPGRADE_STRATEGY} STREQUAL "NO_SWAP")