HAL_PX4: added different modes for external SPI

and lower bus speed to 1MHz

libraries/AP_HAL_PX4/SPIDevice.cpp

@@ -85,16 +85,19 @@ SPIDesc SPIDeviceManager::device_table[] = {
 
 #ifdef PX4_SPI_BUS_EXT
 #ifdef PX4_SPIDEV_EXT0
-    SPIDesc("external0",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT0, SPIDEV_MODE3, 5*MHZ, 5*MHZ),
+    SPIDesc("external0m0",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT0, SPIDEV_MODE0, 2*MHZ, 2*MHZ),
+    SPIDesc("external0m1",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT0, SPIDEV_MODE1, 2*MHZ, 2*MHZ),
+    SPIDesc("external0m2",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT0, SPIDEV_MODE2, 2*MHZ, 2*MHZ),
+    SPIDesc("external0m3",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT0, SPIDEV_MODE3, 2*MHZ, 2*MHZ),
 #endif
 #ifdef PX4_SPIDEV_EXT1
-    SPIDesc("external1",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT1, SPIDEV_MODE3, 5*MHZ, 5*MHZ),
+    SPIDesc("external1",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT1, SPIDEV_MODE3, 2*MHZ, 2*MHZ),
 #endif
 #ifdef PX4_SPIDEV_EXT2
-    SPIDesc("external2",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT2, SPIDEV_MODE3, 5*MHZ, 5*MHZ),
+    SPIDesc("external2",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT2, SPIDEV_MODE3, 2*MHZ, 2*MHZ),
 #endif
 #ifdef PX4_SPIDEV_EXT3
-    SPIDesc("external3",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT3, SPIDEV_MODE3, 5*MHZ, 5*MHZ),
+    SPIDesc("external3",    PX4_SPI_BUS_EXT, (spi_dev_e)PX4_SPIDEV_EXT3, SPIDEV_MODE3, 2*MHZ, 2*MHZ),
 #endif
 #endif