firmware: ti_sci: Mark driver as non removable

The TI-SCI message protocol provides a way to communicate between
various compute processors with a central system controller entity. It
provides the fundamental device management capability and clock control
in the SOCs that it's used in.

The remove function failed to do all the necessary cleanup if
there are registered users. Some things are freed however which
likely results in an oops later on.

Ensure that the driver isn't unbound by suppressing its bind and unbind
sysfs attributes. As the driver is built-in there is no way to remove
device once bound.

We can also remove the ti_sci_remove call along with the
ti_sci_debugfs_destroy as there are no callers for it any longer.

Fixes: aa276781

 ("firmware: Add basic support for TI System Control Interface (TI-SCI) protocol")
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Closes: https://lore.kernel.org/linux-arm-kernel/20230216083908.mvmydic5lpi3ogo7@pengutronix.de/
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Dhruva Gole <d-gole@ti.com>
Link: https://lore.kernel.org/r/20230921091025.133130-1-d-gole@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>