[uart] Make rx pin respect pullup and pulldown settings (#9248)

esphome/components/uart/uart_component_esp8266.cpp

@@ -56,6 +56,13 @@ uint32_t ESP8266UartComponent::get_config() {
 }
 
 void ESP8266UartComponent::setup() {
+  if (this->rx_pin_) {
+    this->rx_pin_->setup();
+  }
+  if (this->tx_pin_ && this->rx_pin_ != this->tx_pin_) {
+    this->tx_pin_->setup();
+  }
+
   // Use Arduino HardwareSerial UARTs if all used pins match the ones
   // preconfigured by the platform. For example if RX disabled but TX pin
   // is 1 we still want to use Serial.