clk: qcom: Fix the rate check during OPP population

The function checks for 'rate' instead 'rrate'. 'rate' is 0 as
initial value therefore OPP populate function returns an error
at the beginning of the for loop.

Change-Id: Ibe82568f3fa9d727faee379eebb37ed40e239d4e
Signed-off-by: Vicky Wallace <vwallace@codeaurora.org>