msm: vidc: Fix video cores clock rate value

No need to half the min frequency in msm_vidc_set_clocks()
if both video cores are used as the min frequency is already
calculated per core basis.

CRs-Fixed: 2154043
Change-Id: I66bbb3e6961b0974a4d5d28bee690a37f7cd9604
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>