misc: tegra-profiler: simpler task status checking

misc: tegra-profiler: simpler task status checking

Use PF_EXITING to check task status and simplify argument checking
in read_all_sources, adjust hrtimer_handler accordingly.

Bug 1625611

Signed-off-by: Dmitry Antipov <dantipov@nvidia.com>
Change-Id: Ida8f9e7ed5492f17868988e05328bfa8432a31e9
Reviewed-on: http://git-master/r/719460
(cherry picked from commit 316d507f4aaa04e9c91da3faa25c861260d6b194)
Reviewed-on: http://git-master/r/748088
GVS: Gerrit_Virtual_Submit
Reviewed-by: Andrey Trachenko <atrachenko@nvidia.com>
Tested-by: Igor Nabirushkin <inabirushkin@nvidia.com>
Reviewed-by: Winnie Hsu <whsu@nvidia.com>