tegra-epl: Set default handshake retry count to 25

commit f13183f9231a011a24b55200f096a12d43f8dc88 from
https://nv-tegra.nvidia.com/r/3rdparty/canonical/linux-jammy.git jetson_36.3

BugLink: https://bugs.launchpad.net/bugs/2049530

This patch add a DT property to set handshake retry count. Default
value is set to 25. On P3898 board, Guest VM resumes quite early
because PCIe controller is disabled. Handshake usually is passing
with 20 but sometimes takes 21 iterations.

https://nvbugs/4190302

Signed-off-by: Rahul Bedarkar <rabedarkar@nvidia.com>
Reviewed-by: Kovid Kumar <kovidk@nvidia.com>
Tested-by: Praveen James <pjames@nvidia.com>
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Jacob Martin <jacob.martin@canonical.com>
Acked-by: Noah Wager <noah.wager@canonical.com>
Signed-off-by: Noah Wager <noah.wager@canonical.com>
Signed-off-by: Rajeshkumar Ramasamy <rajeshkumar.ramasamy@windriver.com>