drivers: misc: grove_lcd: drop GROVE_LCD_NAME

Since the driver is now Devicetree based there are better ways to obtain
a reference to the device: use the DT node label with DEVICE_DT_GET or
continue using device_get_binding with the label defined in DT (an
arbitrary value).

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>