clk: qcom: clk-cpu-osm: Add logic to read the efuse register for L3

The efuse register is never filled for the L3 clock on SDM845.
Add logic to do so. In addition, correct the logic to derive
the speedbin to use.

Change-Id: I3c499fd348e9504b7fdd41f37c22b1f814582d22
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>