RFR: 8287396 LIR_Opr::vreg_number() and data() can return negative number

[Dean Long]

This PR does two things:
- reverts the incorrect change to non_data_bits that included pointer_bits
- treats the data() as an unsigned int to prevent a high bit being treated as a negative number

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Commit messages:
 - remove pointer_bits from non_data_bits

Changes: https://git.openjdk.java.net/jdk/pull/8912/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8912&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287396
  Stats: 6 lines in 1 file changed: 0 ins; 1 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8912.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8912/head:pull/8912

PR: https://git.openjdk.java.net/jdk/pull/8912