pinctrl: berlin: comment the spi functions

Add comments for the SPI functions, to distinguish CLK, SDI, SDO and
C{0,1,2,3}n.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --cc drivers/pinctrl/berlin/berlin-bg2.c
Simple merge

diff --cc drivers/pinctrl/berlin/berlin-bg2cd.c
Simple merge

diff --cc drivers/pinctrl/berlin/berlin-bg2q.c
Simple merge