target-alpha: Add custom PALcode image for CLIPPER emulation.

Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/pc-bios/README b/pc-bios/README
index 02651fe..4d1d816 100644
--- a/pc-bios/README
+++ b/pc-bios/README
@@ -32,3 +32,6 @@
 - The S390 zipl loader is an addition to the official IBM s390-tools
   package. That fork is maintained in its own git repository at:
   git://repo.or.cz/s390-tools.git
+
+- The sources for the Alpha palcode image is available from:
+  git://repo.or.cz/qemu-palcode.git