serial: tegra: set maximum num of uart ports to 8

Set maximum number of UART ports to 8 as older chips have 5 ports and
Tergra186 and later chips will have 8 ports. Add this info to chip
data. Read device tree compatible of this driver and register uart
driver with max ports of matching chip data.

Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>
Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
Link: https://lore.kernel.org/r/1567572187-29820-8-git-send-email-kyarlagadda@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>