dsp: remove float operations in excursion calculation

Avoid float operation during excursion calculation
since that impacts CPU performance. Maintain the
same precision for 2 digit as per requirement
for final value to print in sys/class node.

Change-Id: I34d0f2e7b9eca499206ee9d30acf0d9121b0442e
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>