Fix SerialUART flush (earlephilhower#215)

earlephilhower · web-flow · commit 27476815ab77 · 2021-06-16T08:25:24.000-07:00
Serial1.flush/Serial2.flush was not waiting for the proper FIFO to clear.
Use the proper call from the Pico SDK.

Thanks to Peter Remias for noting it.
diff --git a/cores/rp2040/SerialUART.cpp b/cores/rp2040/SerialUART.cpp
@@ -161,7 +161,7 @@ void SerialUART::flush() {
     if (!_running || !m) {
         return;
     }
-    uart_default_tx_wait_blocking();
+    uart_tx_wait_blocking(_uart);
 }
 
 size_t SerialUART::write(uint8_t c) {

Original file line number	Diff line number	Diff line change
`@@ -161,7 +161,7 @@ void SerialUART::flush() {`
`161`	`161`	`if (!_running \|\| !m) {`
`162`	`162`	`return;`
`163`	`163`	`}`
`164`		`- uart_default_tx_wait_blocking();`
	`164`	`+ uart_tx_wait_blocking(_uart);`
`165`	`165`	`}`
`166`	`166`
`167`	`167`	`size_t SerialUART::write(uint8_t c) {`