uboot-sifiveu: add bootloader package for SiFive Ux40 boards

Add new package for building bootloader for the SiFive U-series boards. Supported
boards at this stage are the HiFive Unleashed and HiFive Unmatched.

Signed-off-by: Zoltan HERPAI <wigyori@uid0.hu>

package/boot/uboot-sifiveu/patches/130-fix-mkimage-host-build.patch

@@ -0,0 +1,24 @@
+--- a/tools/image-host.c
++++ b/tools/image-host.c
+@@ -1125,6 +1125,7 @@ static int fit_config_add_verification_d
+  * 2) get public key (X509_get_pubkey)
+  * 3) provide der format (d2i_RSAPublicKey)
+  */
++#ifdef CONFIG_TOOLS_LIBCRYPTO
+ static int read_pub_key(const char *keydir, const void *name,
+ 			unsigned char **pubkey, int *pubkey_len)
+ {
+@@ -1178,6 +1179,13 @@ err_cert:
+ 	fclose(f);
+ 	return ret;
+ }
++#else
++static int read_pub_key(const char *keydir, const void *name,
++			unsigned char **pubkey, int *pubkey_len)
++{
++	return -ENOSYS;
++}
++#endif
+ 
+ int fit_pre_load_data(const char *keydir, void *keydest, void *fit)
+ {