Fix syntax error

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/boot/mynewt/include/mynewt/config.h b/boot/mynewt/include/mynewt/config.h
index 19cecf2..5d282b7 100644
--- a/boot/mynewt/include/mynewt/config.h
+++ b/boot/mynewt/include/mynewt/config.h
@@ -33,7 +33,7 @@
 #if MYNEWT_VAL(BOOTUTIL_SIGN_RSA)
 #define MCUBOOT_SIGN_RSA 1
 #endif
-#if MYNEWT_VAL(BOOTUTIL_RSA_PKCS1_15
+#if MYNEWT_VAL(BOOTUTIL_RSA_PKCS1_15)
 #define MCUBOOT_RSA_PKCS1_15 1
 #endif
 #if MYNEWT_VAL(BOOTUTIL_SIGN_EC)