mgmt/mcumgr: Remove redundant config headers

The shell_mgmt_config.h and stat_mgmt_config.h as they have been only
providing alternative identifiers for Kconfig options.
Now the Kconfig options are directly used in code and the headers
have been removed.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>
4 files changed