ARM: imx25-pinfunc: remove SION from all modes

With the SION bit set a pin can be read as GPIO even though it's not muxed
as GPIO. This is useful at times. The downside however is that the signal
is not only routed to the GPIO IP but also all other IPs that can make use
of the pin. This resulted in more than one issue for me in the past. Things
like spi transfers that result in usb reenumeration or setting a GPIO to a
value that triggers an RTS irq for an UART.

This convinces me that the SION bit does more harm than good and so all
SION bits are removed that are not known to be needed.

Note that this has no influence on GPIOs under Linux as the gpio-mxc
driver just reports the level the pin is driven to for outputs and not
the level as seen on the pin.

If this commit introduces a regression for you, please report which SION
bit is essential for your setup.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>