The variables 'first' and 'next' in function 'stats_buffer_list_first()'
and 'stats_buffer_list_next()' were potentially used uninitialized.
Depending on the compiler and target architecture, this can lead to
different behavior, including warnings or errors when using strict
warning flags.
By initializing these pointers to 'NULL', we ensure consistent and
expected behavior across all toolchains and configurations.
Signed-off-by: Fabian Kainka <kainka@cognid.de>
Add statistics module which tracks the usage of modem backend
transmit/receive buffers if implemented by a backend.
A modem backend may register itself to the modem backend
stat module, and advertise its transmit and receive buffer
sizes and momentary usage (length).
The modem backend module tracks the maximum usage, which can be
output to the shell using the "modem_stats buffer" shell command.
Signed-off-by: Bjarki Arge Andreasen <bjarki@arge-andreasen.me>
