[2.0.x] LPC176x Serial cleanup (#11032)

Marlin/src/HAL/HAL_LPC1768/HardwareSerial.cpp

Marlin/src/HAL/HAL_LPC1768/HardwareSerial.h

Marlin/src/HAL/HAL_LPC1768/LPC1768_Servo.cpp

Marlin/src/HAL/HAL_LPC1768/SoftwareSPI.cpp

Marlin/src/HAL/HAL_LPC1768/SoftwareSerial.cpp

Marlin/src/HAL/HAL_LPC1768/SoftwareSerial.h

...rc/HAL/HAL_LPC1768/include/digipot_mcp4451_I2C_routines.c

Marlin/src/HAL/HAL_LPC1768/include/serial.h

Marlin/src/HAL/HAL_LPC1768/lpc1768_flag_script.py

Marlin/src/HAL/HAL_LPC1768/main.cpp

Marlin/src/pins/pins_MKS_SBASE.h

frameworks/CMSIS/LPC1768/lib/Print.h

frameworks/CMSIS/LPC1768/lib/Stream.h

frameworks/CMSIS/LPC1768/lib/usb/cdcuser.cpp

frameworks/CMSIS/LPC1768/system/LPC1768.ld

frameworks/CMSIS/LPC1768/system/startup_LPC17xx.S

frameworks/CMSIS/LPC1768/system/system_LPC17xx.c