libxc: correct error message in xc_sr_common.c

When the record length for sending the p2m frames in a migration
stream is too large, the issued error message is not very helpful:

xc: Record (0x00000003, x86 PV P2M frames) length 0x8 exceeds max
    (0x800000): Internal error

When printing the error use the size which was tested instead that of
the record header length.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/libxc/xc_sr_common.c

@@ -71,8 +71,8 @@ int write_split_record(struct xc_sr_context *ctx, struct xc_sr_record *rec,
 
     if ( record_length > REC_LENGTH_MAX )
     {
-        ERROR("Record (0x%08x, %s) length %#x exceeds max (%#x)", rec->type,
-              rec_type_to_str(rec->type), rec->length, REC_LENGTH_MAX);
+        ERROR("Record (0x%08x, %s) length %#zx exceeds max (%#x)", rec->type,
+              rec_type_to_str(rec->type), record_length, REC_LENGTH_MAX);
         return -1;
     }