devicetree: bindings: Make msm8974-pinctrl documentation match code

The compatible string doesn't have an x in it. Fix it. Also
remove the "qcom" prefix from pins and functions as this binding
uses the generic pinctrl bindings for the pins and functions.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>