msm: vidc: Fix errors in governor's formula for AB calculation

There were a couple of errors in the formula.  The first was that in
certain conditions, integer division caused the encoder line buffer
bandwidth to be calculated incorrectly.  This was corrected by converting
the integer division to a fixedpoint division.

The second was that encoder VMEM dpb read formula didn't take into
account the available VMEM for P-frames.

Change-Id: I2f8d9b4963a56a78bab98562568f05630d2b2978
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>