x86: Support jumping to a UPL image

Add a function to allow x86 boards to jump to a UPL images. Currently
only 32-bit entry is supported.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/lib/bootm.c

@@ -259,3 +259,14 @@ int do_bootm_linux(int flag, struct bootm_info *bmi)
 
 	return boot_jump_linux(images);
 }
+
+int arch_upl_jump(ulong entry, const struct abuf *buf)
+{
+	typedef EFIAPI void (*h_func)(void *hoff);
+	h_func func;
+
+	func = (h_func)(ulong)entry;
+	func(buf->data);
+
+	return -EFAULT;
+}