usbc_intr_task: Cond compile pd_shared_alert_task
usbc_intr_task: Cond compile pd_shared_alert_task

The pd_shared_alert_task() function gets compiled in Zephyr EC
regardless of its usage via the CONFIG_HAS_TASK_PD_INT_SHARED resulting
in inaccurate coverage results for boards without its usage.

Compile pd_shared_alert_task() if one of the following is met:

* Using Legacy-EC (No Zephyr)
* CONFIG_HAS_TASK_PD_INT_SHARED is enabled

BRANCH=none
BUG=none
TEST=zmake build -a
TEST=./twister --clobber -i -T zephyr/test/
TEST=make runhosttests -j
TEST=CQ

Signed-off-by: Aaron Massey <79529a820df71f45023239a3663736629646cc34@google.com>
Change-Id: I6c96b3994bb3e5e8d64f3f172012bd42f7fcf21e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3908157
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Code-Coverage: Zoss <345cf107e82c70959d46f59d98bddc98ce458aff@prod.google.com>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec