nic: Fix incorrect wrap handling of RX circular buffer

nic: move other nic functions into the dedicated nic files
uip: alloc buffer multiple of 8 bytes

Signed-off-by: João Silva <jgc3silva@gmail.com>

rtl837x_nic.h

@@ -0,0 +1,20 @@
+#ifndef RTL837X_NIC_H
+#define RTL837X_NIC_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+// #define RXTXDBG 1
+
+bool nic_rx_header(uint16_t ring_ptr) __reentrant;
+bool nic_rx_packet(__xdata uint8_t *buffer, uint16_t ring_ptr) __reentrant;
+
+/* buffer starts at the eight-byte NIC descriptor; len excludes that
+ * descriptor. ring_ptr is the ASIC TX position in eight-byte slots. */
+void nic_tx_packet(__xdata uint8_t *buffer, uint16_t len, uint16_t ring_ptr);
+
+/* RX DMA in eight-byte units. ring_ptr must start inside the configured
+ * RX ring; the hardware wraps transfers that cross its end. */
+bool nic_rx_dma(__xdata uint8_t *buffer, uint16_t ring_ptr, uint8_t words) __reentrant;
+
+#endif