misc: nct1008: fix NULL ptr access in get_trend

misc: nct1008: fix NULL ptr access in get_trend

Return a stable trend when trend is queried during boot before
all the pointers are initialized.

Bug 200311672

Change-Id: I6b03b266b868ac1bd6e39ea63078d24e273bc327
Signed-off-by: Srikar Srimath Tirumala <srikars@nvidia.com>
Reviewed-on: http://git-master/r/1488401
(cherry picked from commit f507b9b74fede1e1adac02c295e0f3666c4a7674)
Signed-off-by: Shreshtha SAHU <ssahu@nvidia.com>
Reviewed-on: http://git-master/r/1492084
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Alex Waterman <alexw@nvidia.com>