thermal: qcom-spmi-temp-alarm: Don't suppress negative temp

Currently driver is suppressing the negative temperature
readings from the vadc. Consumers of the thermal zones need
to read the negative temperature too. Don't suppress the
readings.

Fixes: c610afaa ("thermal: Add QPNP PMIC temperature alarm driver")
Signed-off-by: Veera Vegivada <vvegivad@codeaurora.org>
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/944856eb819081268fab783236a916257de120e4.1596040416.git.gurus@codeaurora.org