Merge common XPT_CALC_GEOMETRY functions into a single convenience function.

Merge common XPT_CALC_GEOMETRY functions into a single convenience function.
Devices below may experience a change in geometry.

* Due to a bug, aic(4) never used extended geometry.  Changes all drives
  >1G to now use extended translation.
* sbp(4) drives exactly 1 GB in size now no longer use extended geometry.
* umass(4) drives exactly 1 GB in size now no longer use extended geometry.

For all other controllers in this commit, this should be a no-op.

PR:
Submitted by:
Looked over by:	scottl
Approved by:
Obtained from:
MFC after: