mod_system_pll: fix incorrect return value
Created by: shriram-k-arm
The fucntion "freq_to_half_cycle_ps" should return unsigned int values only. But the condition that checks whether the given frequency is a multiple of 1 KHz, will return FWK_E_PARAM which is -1. So return 0 instead of FWK_E_PARAM, if the condition fails.
Change-Id: Ib31b65757ec3824ed945a4ac5a8e4abdf860e4a7 Signed-off-by: Shriram K shriram.k@arm.com