clk: iproc: Remove redundant check

Remove the redundant check of 'rate' in the if statement of the
'pll_set_rate' function

Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Fixes: 5fe225c1 ("clk: iproc: add initial common clock support")
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>