m68k: Fix warnings with gcc 4.6

Most of the warnings seem to be related to using 'int' for size_t. Change
this and fix up the remaining warnings and problems. For bootm, the warning
was masked by others, and there is an actual bug in the code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/fpga/xilinx.c b/drivers/fpga/xilinx.c
index 3795c1a..adb4b8c 100644
--- a/drivers/fpga/xilinx.c
+++ b/drivers/fpga/xilinx.c
@@ -220,9 +220,9 @@
 			printf ("Unsupported interface type, %d\n", desc->iface);
 		}
 
-		printf ("Device Size:   \t%d bytes\n"
-				"Cookie:        \t0x%x (%d)\n",
-				desc->size, desc->cookie, desc->cookie);
+		printf("Device Size:   \t%zd bytes\n"
+		       "Cookie:        \t0x%x (%d)\n",
+		       desc->size, desc->cookie, desc->cookie);
 		if (desc->name)
 			printf("Device name:   \t%s\n", desc->name);