mfd: omap-usb-host: Update DT clock binding information

The omap-usb-host driver expects certained named clocks.
Add this information to the DT binding document.

Acked-by: Tony Lindgren <[e-mail]>
Signed-off-by: Roger Quadros <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

Documentation/devicetree/bindings/mfd/omap-usb-host.txt

···
 - single-ulpi-bypass: Must be present if the controller contains a single
   ULPI bypass control bit. e.g. OMAP3 silicon <= ES2.1
 
+- clocks: a list of phandles and clock-specifier pairs, one for each entry in
+  clock-names.
+
+- clock-names: should include:
+  For OMAP3
+  * "usbhost_120m_fck" - 120MHz Functional clock.
+
+  For OMAP4+
+  * "refclk_60m_int" - 60MHz internal reference clock for UTMI clock mux
+  * "refclk_60m_ext_p1" - 60MHz external ref. clock for Port 1's UTMI clock mux.
+  * "refclk_60m_ext_p2" - 60MHz external ref. clock for Port 2's UTMI clock mux
+  * "utmi_p1_gfclk" - Port 1 UTMI clock mux.
+  * "utmi_p2_gfclk" - Port 2 UTMI clock mux.
+  * "usb_host_hs_utmi_p1_clk" - Port 1 UTMI clock gate.
+  * "usb_host_hs_utmi_p2_clk" - Port 2 UTMI clock gate.
+  * "usb_host_hs_utmi_p3_clk" - Port 3 UTMI clock gate.
+  * "usb_host_hs_hsic480m_p1_clk" - Port 1 480MHz HSIC clock gate.
+  * "usb_host_hs_hsic480m_p2_clk" - Port 2 480MHz HSIC clock gate.
+  * "usb_host_hs_hsic480m_p3_clk" - Port 3 480MHz HSIC clock gate.
+  * "usb_host_hs_hsic60m_p1_clk" - Port 1 60MHz HSIC clock gate.
+  * "usb_host_hs_hsic60m_p2_clk" - Port 2 60MHz HSIC clock gate.
+  * "usb_host_hs_hsic60m_p3_clk" - Port 3 60MHz HSIC clock gate.
+
 Required properties if child node exists:
 
 - #address-cells: Must be 1