add Xilinx_abort_fn to Xilinx_Spartan3_Slave_Serial_fns

Currently the hardware was left in an undefined state in case Spartan3
serial load failed. This patch adds Xilinx_abort_fn to give the board
a possibility to clean up in this case.

Signed-off-by: Wolfgang Wegner <w.wegner@astro-kom.de>
diff --git a/include/spartan3.h b/include/spartan3.h
index d5a589d..0f0b400 100644
--- a/include/spartan3.h
+++ b/include/spartan3.h
@@ -58,6 +58,7 @@
 	Xilinx_wr_fn	wr;
 	Xilinx_post_fn	post;
 	Xilinx_bwr_fn	bwr; /* block write function */
+	Xilinx_abort_fn abort;
 } Xilinx_Spartan3_Slave_Serial_fns;
 
 /* Device Image Sizes