Build failure if PPP and mbed trace or L3IPInterface is enabled

[kivaisan]

Description of defect

Build will fail if mbed traces and PPP, or L3IPInterface is enabled due to missing intergration to #11942

Cellular trace needs to be fixed to use SocketAddress:
https://github.com/ARMmbed/mbed-os/blob/master/features/cellular/framework/AT/AT_CellularContext.cpp#L988

L3IPInterface: This method needs to be changed to use new SocketAddress:
https://github.com/ARMmbed/mbed-os/blob/master/features/netsocket/L3IPInterface.cpp#L42-L54

Target(s) affected by this defect ?

All

Toolchain(s) (name and version) displaying this defect ?

All

What version of Mbed-os are you using (tag or sha) ?

mbed-os-99.99.99 (8f1bf96)

What version(s) of tools are you using. List all that apply (E.g. mbed-cli)

Mbed-cli

How is this defect reproduced ?

Enable mbed-trace and PPP, or L3IPInterface

cc: @michalpasztamobica

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOTRIAGE-2556

[ciarmcom]

Thank you for raising this detailed GitHub issue. I am now notifying our internal issue triagers.
Internal Jira reference: https://jira.arm.com/browse/IOTOSM-2220