RFR: No caching of can fast result

[Robbin Ehn]

can_freeze_fast() result could be changed byt JRT_BLOCK.
Let's not cache it.

-------------

Commit messages:
 - No caching of can fast result

Changes: https://git.openjdk.java.net/loom/pull/157/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=157&range=00
  Stats: 4 lines in 1 file changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/loom/pull/157.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/157/head:pull/157

PR: https://git.openjdk.java.net/loom/pull/157