bmi160: add C driver and example. Add SPI support, other improvments.

This adds SPI support to the BMI160, as well as a C driver and a C
example.  In addition, some changes were made to more properly detect
and handle errors.

Functions supplied by the bosch_bmi160 driver source code is also
exported and made available to callers who want more than what the
basic driver support.  Bus access methods (I2C and SPI) are also now
exposed to both C and C++.

Signed-off-by: Jon Trulson <jtrulson@ics.com>

src/bmi160/CMakeLists.txt

@@ -1,5 +1,9 @@
-set (libname "bmi160")
-set (libdescription "Bosch BMI160 Accelerometer, Gyroscope and BMM150 Magnetometer")
-set (module_src ${libname}.cxx bosch_bmi160.c)
-set (module_hpp ${libname}.hpp)
-upm_module_init()
+upm_mixed_module_init (NAME bmi160
+    DESCRIPTION "UPM driver for the BMI160 accel/gyro/mag"
+    C_HDR bmi160.h bosch_bmi160.h
+    C_SRC bmi160.c bosch_bmi160.c
+    CPP_HDR bmi160.hpp
+    CPP_SRC bmi160.cxx
+#    FTI_SRC bmi160_fti.c
+    CPP_WRAPS_C
+    REQUIRES mraa)