gmac - fix hang in Ethernet driver (#19)

Ethernet driver is hanging. Occurs due to rollover of statistics, which
triggers an interrupt, and we never clear the interrupt's status.

Quick fix is to just freeze the statistics, and then they never trigger
interrupts.

Additional change: disable interrupts while the DPC is pending. This
noticeably improves performance.

README.md

@@ -26,7 +26,7 @@ This repository contains drivers for RK35xx-based platforms, with a focus on RK3
 |Multimedia codecs||🔴 Not working||
 |DSI||🔴 Not working||
 |CSI||🔴 Not working||
-|GMAC Ethernet|[dwc_eqos](https://github.com/worproject/Rockchip-Windows-Drivers/tree/master/drivers/net/dwc_eqos)|🟢 Working||
+|GMAC Ethernet|[dwc_eqos](drivers/net/dwc_eqos)|🟡 Partially working|1000Mbps only (gigabit Ethernet only - 10/100 not yet supported)|
 |UART||🔴 Not working|No OS driver but debugging does work on UART2, being configured by UEFI.|
 |GPIO|[rk3xgpio](https://github.com/worproject/Rockchip-Windows-Drivers/tree/master/drivers/gpio)|🟢 Working||
 |I2C|[rk3xi2c](https://github.com/worproject/Rockchip-Windows-Drivers/tree/master/drivers/i2c)|🟢 Working||