clk: qcom: 8939: Add clock definitions

Add pcnoc_usb_a_clk, snoc_usb_a_clk, bimc_usb_a_clk clocks
for nominal voting support on 8939 target.

CRs-Fixed: 722888
Change-Id: I53ff40b25a06c35b67ac07134f5937c4d4573e7a
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>