[interp] Reduce register pressure in endfinally.

[interp] Reduce register pressure in endfinally.
Eventually this could contribute to stack savings. On its own, nothing.
The compiler apparently likes to create temporaries, like ip and ip - 1.
Which then have to survive functions calls, on the stack, if nonvolatile registers are exhausted.
This combats that and in a larger PR helped.

Commit migrated from https://github.com/mono/mono/commit/f4c1358ed0c496865c24ee32efa498ace0e8ed5e