RFR: 8237882: ZGC: Removed ZUtils::round_{up,down}_power_of_2() declarations

[Kim Barrett]

> On Jan 27, 2020, at 8:54 AM, Per Liden <per.liden at oracle.com> wrote:
> 
> JDK-8234331 removed ZUtils::round_{up,down}_power_of_2() but left the function declarations in the ZUtils class.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8237882
> Webrev: http://cr.openjdk.java.net/~pliden/8237882/webrev.0
> 
> /Per

Looks good.