Add fixed-point temp calculation as backup option.
Add fixed-point temp calculation as backup option.

We prefer to use floating-point version but we might need fixed-point
version in the future if we don't have FPU support. If CONFIG_FPU flag
is not set, fixed-point object temperature calculation would be used.

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

BUG=chrome-os-partner:7801
TEST=none

Change-Id: I69364b10bedf1351206e52266d669b4c566bd6f6

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