pinctrl: mvebu: armada-370: fix spi0 pin description

Due to a mistake, the CS0 and CS1 SPI0 functions were incorrectly
named "spi0-1" instead of just "spi0". This commit fixes that.

This DT binding change does not affect any of the in-tree users.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: <stable@vger.kernel.org> # v3.7+
Fixes: 5f597bb2 ("pinctrl: mvebu: add pinctrl driver for Armada 370")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>