board: hpe: gxp: add HPE GXP soc support

Add basic support for the HPE GXP SoC. Reset the EHCI controller at
boot.

Signed-off-by: Nick Hawkins <nick.hawkins@hpe.com>
diff --git a/board/hpe/gxp/Makefile b/board/hpe/gxp/Makefile
new file mode 100644
index 0000000..775d6bf
--- /dev/null
+++ b/board/hpe/gxp/Makefile
@@ -0,0 +1 @@
+obj-y += gxp_board.o