thermal: tsens: switch from of_iomap() to devm_ioremap_resource()

devm_ioremap_resources() automatically requests resources (so that the I/O
region shows up in /proc/iomem) and devm_ wrappers do better error handling
and unmapping of the I/O region when needed.

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>