riscv: t-head: licheepi4a: initial support added

Add support for Sipeed's Lichee Pi 4A board which based on T-HEAD's
TH1520 SoC, only minimal device tree and serial console are enabled,
so it's capable of chain booting from T-HEAD's vendor u-boot.

Reviewed-by: Wei Fu <wefu@redhat.com>
Signed-off-by: Yixun Lan <dlan@gentoo.org>
diff --git a/board/thead/th1520_lpi4a/Makefile b/board/thead/th1520_lpi4a/Makefile
new file mode 100644
index 0000000..9671b3b
--- /dev/null
+++ b/board/thead/th1520_lpi4a/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (c) 2023, Yixun Lan <dlan@gentoo.org>
+
+obj-y += board.o