Add UFS Host Controller to the list of generic node names

UFS Host Controller (ufshc) is reponsible for managing the interface
between host SW stack and UFS device.

In a lot of places, 'ufs' is used as the node name to identify the host
controller, but it is wrong since 'ufs' denotes 'UFS device'.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Author: Mani-Sadhasivam

source/chapter2-devicetree-basics.rst

@@ -292,6 +292,7 @@ name should be one of the following choices:
    * timer
    * touchscreen
    * tpm
+   * ufshc
    * usb
    * usb-hub
    * usb-phy