[EDG-4952] Default value if does not exist in DB.

[EGD-4952] Added stetings for battery critical level

[EGD-4952] Cleanup

[EGD-4952] Moved battery level check to separate module

[EGD-4952] Fixes for rt1051

[EGD-4952] Added battery check at init and if crit level changed

[EGD-4952] Added critical level check + messages

Merge branch 'stable'

update changelog for v0.51.1

[EGD-5009] Change messy callback logic in audio module

Refactor audio module to use only one callback for communication
with audio service. This also simplifies the logic and removes
necessity to define defaults for audio values in multiple places.

[EGD-5022] Fix invalid open flags in vfscore

Opening file with O_CREAT mode on the mounted fat filesystem
should create file if doesn't exist. Currently it returns ENOENT
This path fix this issue. ff_fat create flags are fixed.

[EGD-5016] Fix vfs-littlefs failed mount init

Fix issue with memory leak during mount in littlefs core
when mount fails.

[EGD-4758] Add lfs object state sync

Add lfs object state sync.

[EGD-4758] Fix includes in littlefs

Fix includes in the littlefs

[EGD-4758] Add block size and fs size

Add blocks size and blocks count detecting
of the file size.

[EGD-4758] Fix littlefs directory iterator

Directory iterator now seams to be working

[EGD-4758] Add unit tests for littlefs

Some tests passed but it needs some work...

[EGD-4758] Fix littlefs boundary check

    Currently littlefs boudary is checked in the wrong place
    this commit fix this issue

[EGD-4758] Add Littlefs unit test

This is an initial implementation of littlefs
unit tests

[EGD-4758] Add Littlefs config

Add littlefs config
Signed-off-by: Lucjan Bryndza <lucjan.bryndza@mudita.com>