Have TMP006 sensor report -1 on sensor failure.
Have TMP006 sensor report -1 on sensor failure.

Temperature reading should be -1 on sensor failure.

Signed-off-by: Vic Yang <victoryang@chromium.org>

BUG=chrome-os-partner:8241
TEST="gpioset enable_vs 0" and "temps" gives "Error"
"gpioset enable_vs 1" and "temps" gives correct reading.

Change-Id: Ide82bd3433d3de12a749b0ee85f1ae1c6b12c5e5

eatbyte/chromium-ec,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,thehobn/ec,alterapraxisptyltd/chromium-ec,gelraen/cros-ec,longsleep/ec,fourier49/BZ_DEV_EC,coreboot/chrome-ec,eatbyte/chromium-ec,thehobn/ec,gelraen/cros-ec,fourier49/BIZ_EC,coreboot/chrome-ec,mtk09422/chromiumos-platform-ec,gelraen/cros-ec,longsleep/ec,longsleep/ec,coreboot/chrome-ec,longsleep/ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BIZ_EC,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,mtk09422/chromiumos-platform-ec,coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,eatbyte/chromium-ec,alterapraxisptyltd/chromium-ec,md5555/ec,md5555/ec,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,alterapraxisptyltd/chromium-ec,gelraen/cros-ec,eatbyte/chromium-ec,coreboot/chrome-ec,fourier49/BZ_DEV_EC,thehobn/ec,fourier49/BZ_DEV_EC,thehobn/ec,fourier49/BIZ_EC,mtk09422/chromiumos-platform-ec,md5555/ec