thermal: exynos: fix setting rising_threshold for Exynos5433

thermal: exynos: fix setting rising_threshold for Exynos5433

BugLink: http://bugs.launchpad.net/bugs/1815234
[ Upstream commit 8bfc218d0ebbabcba8ed2b8ec1831e0cf1f71629 ]

Add missing clearing of the previous value when setting rising
temperature threshold.

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>