I am a bit confused. In your shp2pgsql command you define the parameters -p which:
Only produces the table creation SQL code, without adding any actual
data. This can be used if you need to completely separate the table
creation and data loading steps.
AND -c which:
Creates a new table and populates it from the Shape file. This is the
I think these are mutually exclusive? Is your table populated with data or you just want to create the structure of the table?
In either case, once the table is created it should also have created a contraint which controls the type of spatial data allowed (point, multipoint, line, etc). The constraint is usually named enforce_geotype_. So you can drop the constraint and create a new one indicating the allowable spatial types (this is assuming that the geometries currently in the table ARE of this type) e.g.
ALTER TABLE Oversiktskartans_texter DROP CONSTRAINT enforce_geotype_shape;
ALTER TABLE Oversiktskartans_texter ADD CONSTRAINT enforce_geotype_shape
CHECK (geometrytype(shape) = 'MULTIPOINT'::text);