Prevent compilation of unused u8g-oriented code

Marlin/src/HAL/HAL_DUE/u8g_com_HAL_DUE_shared_hw_spi.cpp

Marlin/src/HAL/HAL_DUE/u8g_com_HAL_DUE_st7920_sw_spi.cpp

Marlin/src/HAL/HAL_LPC1768/u8g_com_HAL_LPC1768_hw_spi.cpp

...in/src/HAL/HAL_LPC1768/u8g_com_HAL_LPC1768_ssd_hw_i2c.cpp

...68/u8g_com_HAL_LPC1768_ssd_sw_i2c.cpp under construction

...src/HAL/HAL_LPC1768/u8g_com_HAL_LPC1768_st7920_hw_spi.cpp

...src/HAL/HAL_LPC1768/u8g_com_HAL_LPC1768_st7920_sw_spi.cpp

Marlin/src/HAL/HAL_LPC1768/u8g_com_HAL_LPC1768_sw_spi.cpp

Marlin/src/lcd/dogm/u8g_dev_ssd1306_sh1106_128x64_I2C.cpp

Marlin/src/lcd/dogm/u8g_dev_st7565_64128n_HAL.cpp

Marlin/src/lcd/dogm/u8g_dev_st7920_128x64_HAL.cpp

Marlin/src/lcd/dogm/u8g_dev_uc1701_mini12864_HAL.cpp

Marlin/src/lcd/dogm/ultralcd_st7920_u8glib_rrd_AVR.cpp

Marlin/src/lcd/lcdprint_u8g.cpp