native.bbclass: drop _virtclass-native and _virtclass-nativesdk overrides
The _virtclass-XXX over-rides are problematic in that they are higher
priority than _forcevariable, which is documented as being the
highest priority over-ride.
Since they are now obsolete (replaced by _class-native and
_class-nativesdk) drop them entirely rather than try to fix their
priority.
Signed-off-by: Andre McCurdy <armccurdy@gmail.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
