phy: cadence: sierra: Remove variable that is not assigned to

phy: cadence: sierra: Remove variable that is not assigned to

In cdns_sierra_pll_bind_of_clocks the variable 'i' is declared but never
assigned to before its value is used in a dev_err. Replace clk_names[i]
by the name passed to device_bind(), i.e., "pll_mux_clk". With that, the
clk_names[] array is unused and can therefore be removed.

This issue was found by Smatch.

Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
[jf: update description]
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>