Fix for duplicate (dead) assignment in util-nvctl.cpp

Static analysis (scan-build) identified a dead assignment
in util-nvctl.cpp, where h was assigned a value, and
assigned (the same) value three lines later.  Delete
the duplicate assignment.
(cherry picked from commit 7a2a48df924debd2ec42246e2c218d289ba60241)

Signed-off-by: Stuart Morgan <smorgan@mythtv.org>