Using a FreeRTOS mutex directly is deprecated.  Replace it with a
`struct mutex`.  Similarly, the deprecated `hwlock_acquire_timeout()`
is replaced with `hwlock_acquire()`.

Signed-off-by: Rahix <rahix@rahix.de>

Rename hwlock_acquire() to hwlock_acquire_timeout() in preparation for
future changes to the hw-lock API.  Change all uses of the hw-lock API
to reflect this change.

This commit does not introduce any functional changes, except getting
rid of the timeout usage warnings.  This change is no-op, because the
hwlock_acquire() implementation already replaces any non-zero timeout
value with portMAX_DELAY.

Signed-off-by: Rahix <rahix@rahix.de>

Fix sign-compare warnings for these constants.

Signed-off-by: Rahix <rahix@rahix.de>

As discussed in card10/firmware!316, this commit prevents I2C lockup by
discarding overflowing samples instead of blocking until they have been
read.  This is not ideal as the samples read will not be the most recent
ones.  A deeper refactor of the sensor-stream internal API can fix this
in the future.

Cc: @flo_h


Signed-off-by: Rahix <rahix@rahix.de>

Signed-off-by: Rahix <rahix@rahix.de>