Commit "weston-log: add function to avoid direct
access to compositor members in non-core code" added the
function weston_compositor_add_log_scope mainly to allow
libweston users to avoid direct accessing core structs, as
weston_compositor.
Replace weston_log_context_add_log_scope usage by
weston_compositor_add_log_scope.
Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>