This patch adds pwm-pca9685.c and pwm-pca9685.h files,
which support access to I2C-based PCA9685 PWM controller
configuration register through a function interface.
The PCA9685 is an I2C-bus controlled 16-channel LED controller
optimized for Red/Green/Blue/Amber (RGBA) color backlighting
applications. Each LED output has its own 12-bit resolution
(4096 steps) fixed frequency individual PWM controller that
operates at a programmable frequency from a typical of 24 Hz to
1526 Hz with a duty cycle that is adjustable from 0 % to 100 %
to allow the LED to be set to a specific brightness value.
More about PCA9685 can be found in its datasheet[1].
This driver is needed in order to configure Galileo pinmux.
[1] - http://www.nxp.com/documents/data_sheet/PCA9685.pdf
