ARM: dts: imx25-pinfunc: add missing and fix wrong SPI related defintions

I used the i.MX25 Reference Manual (Rev 2 01/2011) as source for these
additions and fixes.

No mainline dts is affected by the fixes (nor obviously by the
additions).

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