mutex: retry immediatly if we could not get exclusive access
mutex: retry immediatly if we could not get exclusive access

When updating the lock field of the mutex to acquire it, if the store
exclusive fails, we want to retry immediatly else if the failure has
been triggered by the other user doing the mutex_unlock we might not be
woken up.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BUG=chrome-os-partner:8492
TEST=run on proto-0.5 and see that the temperature sensor and battery
tasks are longer hanging (see the bug for details how to check it)

Change-Id: I0c8a4e997666a7781b3837f0dbbc47ffbc06b6c3

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