examples: Simplify some of the examples

Instead of using `Kaleidoscope.serialPort()` in every example, introduce a
helper variable in some cases, to make the coder nicer to read.

Signed-off-by: Gergely Nagy <algernon@keyboard.io>

examples/Features/EEPROM/EEPROM-Settings/EEPROM-Settings.ino

@@ -42,16 +42,18 @@ KEYMAPS(
 KALEIDOSCOPE_INIT_PLUGINS(EEPROMSettings);
 
 void setup() {
-  Kaleidoscope.serialPort().begin(9600);
+  auto &serial_port = Kaleidoscope.serialPort();
+
+  serial_port.begin(9600);
 
   Kaleidoscope.setup();
 
-  while (!Kaleidoscope.serialPort()) {
+  while (!serial_port) {
   }
 
-  Kaleidoscope.serialPort().println(EEPROMSettings.isValid() ? F("valid EEPROM settings") : F("invalid EEPROM settings"));
-  Kaleidoscope.serialPort().println(EEPROMSettings.crc(), HEX);
-  Kaleidoscope.serialPort().println(EEPROMSettings.version());
+  serial_port.println(EEPROMSettings.isValid() ? F("valid EEPROM settings") : F("invalid EEPROM settings"));
+  serial_port.println(EEPROMSettings.crc(), HEX);
+  serial_port.println(EEPROMSettings.version());
 }
 
 void loop() {

examples/Features/HostOS/HostOS.ino

@@ -43,12 +43,14 @@ KEYMAPS(
 KALEIDOSCOPE_INIT_PLUGINS(EEPROMSettings, HostOS);
 
 void setup() {
-  Kaleidoscope.serialPort().begin(9600);
+  auto &serial_port = Kaleidoscope.serialPort();
+
+  serial_port.begin(9600);
 
   Kaleidoscope.setup();
 
-  Kaleidoscope.serialPort().print("Host OS id is: ");
-  Kaleidoscope.serialPort().println(HostOS.os(), DEC);
+  serial_port.print("Host OS id is: ");
+  serial_port.println(HostOS.os(), DEC);
 }
 
 void loop() {

examples/Keystrokes/Leader/Leader.ino

@@ -39,12 +39,14 @@ KEYMAPS(
 )
 // *INDENT-ON*
 
+auto &serial_port = Kaleidoscope.serialPort();
+
 static void leaderTestA(uint8_t seq_index) {
-  Kaleidoscope.serialPort().println(F("leaderTestA"));
+  serial_port.println(F("leaderTestA"));
 }
 
 static void leaderTestAA(uint8_t seq_index) {
-  Kaleidoscope.serialPort().println(F("leaderTestAA"));
+  serial_port.println(F("leaderTestAA"));
 }
 
 static const kaleidoscope::plugin::Leader::dictionary_t leader_dictionary[] PROGMEM =