Synchronize with UGW-8.1.1.20 for DSL related packages

Compare contents of all related packages between the current one and those in UGW-8.1.1.20.

Driver, API, control applications, aca and ppe firmware
dsl-cpe-control-vrx - 4.20.1.2 to 4.20.1.2.0
dsl-cpe-api-vrx     - 4.20.1.2 to 4.20.1.2.0
dsl-cpe-fapi        - 0.6.1 to 0.6.1.1.0
dsl-cpe-mei-vrx     - 1.8.1.1 to 1.8.1.1.0
vrx518_aca_fw       - No need to update since they are the same
vrx518_ppe_fw       - No need to update since they are the same
vrx518_tc_drv       - No need to update since they are the same

Dependencies
libscapi            - No need to update since they are the same
libhelper           - No need to update since they are the same
fapi_system         - Update the Makefile to define CONFIG_VRX518_SUPPORT properly
ifxos               - No need to update since they are the same

Note that DSL firmware is updated in targets git repo.