The 2nd patch, while originally having been the main piece here, and while
fixing a bug kind of as a side effect, is partly RFC; see there. The last
two changes are really minor adjustments for aspects noticed while putting
together the main change.

1: provide an inverted Kconfig control for shim-exclusive mode
2: common: reduce PV shim footprint
2: don't even allow enabling GRANT_TABLE
3: suppress core-parking logic

The main change in v2 is the addition of patch 1, as requested by Andrew.

Jan