MT#56465 Make `sdp_ng_flags` non-const for `sdp_create()`
In order to be able to use similar attributes manipulations
as in the `sdp_replace()` (based on the `sdp_ng_flags`)
a non-const parameter is required.
Change-Id: I4dce1edfa16b0c2dcd9315a2a3d8cc585f32858f