dt: bindings: vendor-prefix: Add 3 accelerometer vendor prefixes

Recently the kernel has gotten support in the iio subsystem for a number
of new accelerometers from mCube, Memsic and MiraMEMS.

This commit adds the vendor prefixes already used for these vendors
in Documentation/devicetree/bindings/i2c/trivial-devices.txt to
vendor-prefixes.txt.

The "full" company names were taken from the company's websites:
http://www.mcubemems.com/
http://www.memsic.com/
http://www.miramems.com/en/



Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>