octeontx2-pf: Fix and simplify IRQ coalescing settings

commit bf8012eebdbe80d61f917e06066588711aebf08c from
git@git.assembla.com:cavium/WindRiver.linux.git

Current logic has +/- 1 of time_wait and mul/div by 10 of
count_wait everywhere which is confusing. Also there are
many scenarios where time_wait is not being set properly.
This patch simplifies the logic and fixes the issues.

Change-Id: If7c51d60fcc708fa9af02c28632b220b6abc5d6b
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/14056


Reviewed-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Tested-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Signed-off-by: Kevin Hao <kexin.hao@windriver.com>