Revert "reset: Add a Gemini reset controller"

This reverts commit 2acb037f.

We ended up merging the reset controller into the clock
controller so we can now get rid of this stand-alone
implementation.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>