dt-bindings: pinctrl: qcom: Add sc7280 pinctrl bindings

Add device tree binding Documentation details for Qualcomm SC7280
TLMM block.

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1604570192-15057-1-git-send-email-rnayak@codeaurora.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>