motion: fix postgresql support

motion: fix postgresql support

The commandline paramter to enable/disable postgresql support is
called '--with-pgsql/--without-pgsql' and not '--with-postgresql/
--without-postgresql'.

Fixes [1] in case postgresql development files are installed on the host:

  checking for PostgreSQL... testing
  checking autodect pgsql headers... yes /usr/include/postgresql
  checking autodect pgsql libs... /usr/lib64
  checking for PQconnectStart in -lpq... no
  configure: error: PostgreSQL support can't build without PostgreSQL libraries

[1] http://autobuild.buildroot.net/results/749/7497730da2affffe0e5b9b790081de10c269f416

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>