dt-bindings: clock: Update the clk for gcc in MONACO

Add the clk id for GCC_USB2_PRIM_CLKREF_CLK in GCC header file
for MONACO.

Change-Id: I9ba826e964cfd4837ba1ece7c182496e6d16a965
Signed-off-by: Saurabh Sahu <sausah@codeaurora.org>