madwifi: napi polling fix

- fix u_int negative comparison
 - add some reserve for polling packets (ff has two frames in one descriptor)


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@12280 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/madwifi/patches/300-napi_polling.patch

@@ -234,7 +234,7 @@
 +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24)
 +		processed++;
 +#endif
-+		if (rx_limit-- < 0) {
++		if (rx_limit-- < 2) {
 +			early_stop = 1;
 +			break;
 +		}