Merge pull request #10725 from jia200x/pr/cc2420_inline_flush

drivers/cc2420: move flush sequence to inline function 

drivers/cc2420/cc2420.c

@@ -158,6 +158,15 @@ void cc2420_tx_exec(cc2420_t *dev)
     }
 }
 
+static inline void _flush_rx_fifo(cc2420_t *dev)
+{
+    /* as stated in the CC2420 datasheet (section 14.3), the SFLUSHRX command
+     * strobe should be issued twice to ensure that the SFD pin goes back to its
+     * idle state */
+    cc2420_strobe(dev, CC2420_STROBE_FLUSHRX);
+    cc2420_strobe(dev, CC2420_STROBE_FLUSHRX);
+}
+
 int cc2420_rx(cc2420_t *dev, uint8_t *buf, size_t max_len, void *info)
 {
     (void)info;
@@ -202,8 +211,7 @@ int cc2420_rx(cc2420_t *dev, uint8_t *buf, size_t max_len, void *info)
         }
 
         /* finally flush the FIFO */
-        cc2420_strobe(dev, CC2420_STROBE_FLUSHRX);
-        cc2420_strobe(dev, CC2420_STROBE_FLUSHRX);
+        _flush_rx_fifo(dev);
     }
 
     return (int)len;