ARM: dts: turris-omnia: Fix mpp26 pin name and comment

ARM: dts: turris-omnia: Fix mpp26 pin name and comment

[ Upstream commit 0879086d32d4a0791a89a32f3b809a5622d25a78 ]

There is a bug in Turris Omnia's schematics, whereupon the MPP[26] pin,
which is routed to CN11 pin header, is documented as SPI CS1, but
MPP[26] pin does not support this function. Instead it controls chip
select 2 if in "spi0" mode.

Fix the name of the pin node in pinctrl node and fix the comment in SPI
node.

Fixes: 36b28c350a9a ("ARM: dts: add support for Turris Omnia")
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>