tegra-epl: Set handshake retry count to 20

commit 62f5c3528df8649b4c079e78f9851026989a90c8 from
https://nv-tegra.nvidia.com/r/3rdparty/canonical/linux-jammy.git jetson_36.3

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

One customer board, EPL handshake failure is observed on resume. It is
observed that Linux guest VM is resuming around 300 milliseconds early
compared to internal board.

With retry count of 10, EPL handshake is passing at 8th attempt. This
patch sets retry count 20 which is sufficiently large enough compared
to what used in tests.

Retry count of 20 brings approx. 100 milliseconds of timeout before
throwing error which is theoretically same compared to what used in
Epd on AV+Q.

While at it, remove kernel thread which is used for just handshake
purpose and perform handshake directly from context of probe and
resume callbacks.

https://nvbugs/4271502

Signed-off-by: Rahul Bedarkar <rabedarkar@nvidia.com>
Reviewed-by: Kovid Kumar <kovidk@nvidia.com>
Reviewed-by: Bruce Yang <kuoyuany@nvidia.com>
Tested-by: Bruce Yang <kuoyuany@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>