mfd: tps65086: Add cell entry for reset driver

The only way to reset the BeagleV Starlight v0.9 board[1] properly is to
tell the PMIC to reset itself which will then assert the external reset
lines of the SoC, USB hub and ethernet phy.

This adds an mfd cell entry for the reset driver doing just that.

[1] https://github.com/beagleboard/beaglev-starlight



Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Lee Jones <lee.jones@linaro.org>