db: Remove obsolete variables
db: Remove obsolete variables

meta/conf/distro/include/seperatebuilddir.inc has been dropped,
so remove B_pn-db and B_pn-db-native.

Signed-off-by: Trung Do <64081e6b7eb2b24289b8a4e51cef9836ddf28af2@toshiba-tsdv.com>

meta-debian/meta-debian,tienlee/meta-debian,tienlee/meta-debian,nghiaht-tsdv/meta-debian,nghiaht-tsdv/meta-debian,tienlee/meta-debian,meta-debian/meta-debian,meta-debian/meta-debian,nghiaht-tsdv/meta-debian,meta-debian/meta-debian,nghiaht-tsdv/meta-debian,tienlee/meta-debian,tienlee/meta-debian,meta-debian/meta-debian,tienlee/meta-debian,meta-debian/meta-debian,nghiaht-tsdv/meta-debian,nghiaht-tsdv/meta-debian