Input termination is not necessary when the LVCMOS_CLK input is driven from a LVCMOS driver that is series-terminated to match the characteristic impedance of the trace. Otherwise, place the input termination resistor as close to the LVCMOS_CLK input as possible.
Avoid or minimize vias in the 50-Ω input trace to minimize impedance discontinuities.
If not used, LVCMOS_CLK input may be left as no connect.