This commit adds LSM330 SPI and ADXL372 drivers.

Squashed merge of the following:

Author: Gregory Nutt <gnutt@nuttx.org>
    drivers/sensors:  Fix some minor typos in last commit that cause some compile problems.
    drivers/sensors/:  Clean up some coding standard isses in LM330 and ADXL372 drivers.
    drivers/sensors/README.txt:  Clean up some long lines and odd line breaks.
    include/nuttx/sensors:  Completes coding style review of adxl372.h, cluster_driver.h, and lsm330.h.

Author: Bob Feretich <bob.feretich@rafresearch.com>
    Add LSM330 SPI and ADXL372 drivers along with the cluster driver infrastructure.