[11u] RFR (S) 8248870: AARCH64: I2L/L2I conversions can be skipped for masked positive values

[Dmitry Chuyko]

Hello,

Original RFE: https://bugs.openjdk.java.net/browse/JDK-8248870

aarch64_ad.m4 and aarch64.ad are decorated slightly different in 11u, 
unmodified ubfizIConvI2LAndI code was inserted similarly after 
ubfizIConvI2L taking that into account, benchmark part applied cleanly.

11u webrev: http://cr.openjdk.java.net/~dchuyko/8248870/webrev.11u.00/

Testing: tier1, tier2.

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Thanks,
-Dmitry