commit e2860e1f ("serial: 8250_of: Add reset support")
introduced reset support for the 8250_of driver.

However it unconditionally uses the assert/deassert pair to
deassert reset on the device at probe and assert it at
remove. This does not work with systems that have a
self-deasserting reset controller, such as Gemini, that
recently added a reset controller.

As a result, the console will not probe on the Gemini with
this message:

Serial: 8250/16550 driver, 1 ports, IRQ sharing disabled
of_serial: probe of 42000000.serial failed with error -524

This (-ENOTSUPP) is the error code returned by the
deassert() operation on self-deasserting reset controllers.

To work around this, implement dummy .assert() and
.deassert() operations in the Gemini combined clock and
reset controller. This fixes the issue on this system.

Cc: Joel Stanley <joel@jms.id.au>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-serial@vger.kernel.org
Fixes: e2860e1f ("serial: 8250_of: Add reset support")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>