gpiolib: Fix references to gpiod_[gs]et_*value_cansleep() variants

Commit 372e722e ("gpiolib: use descriptors internally") renamed
the functions to use a "gpiod" prefix, and commit 79a9becd
("gpiolib: export descriptor-based GPIO interface") introduced the "raw"
variants, but both changes forgot to update the comments.

Readd a similar reference to gpiod_set_value(), which was accidentally
removed by commit 1e77fc82 ("gpio: Add missing open drain/source
handling to gpiod_set_value_cansleep()").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20190701142738.25219-1-geert+renesas@glider.be


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>