RFR: 8264412: AArch64: CPU description should refer DMI [v4]

[Yasumasa Suenaga]

> `jdk.CPUInformation` event on AArch64 has valid CPU description in [JDK-8262491](https://bugs.openjdk.java.net/browse/JDK-8262491), however it does not work on UEFI booted machine.
> 
> [JDK-8262491](https://bugs.openjdk.java.net/browse/JDK-8262491) refers device tree to get board name, however it does not exist on UEFI. We need to refer DMI.
> However we need to have root privilege, so we refer /sys/devices/virtual/dmi/id to avoid it.
> 
> We can get board name from /sys/devices/virtual/dmi/id/board_name, but some machine set empty string to it. So we will refer /sys/devices/virtual/dmi/id/product_name as a fallback.
> 
> For example, we can get following CPU description on AWS A1 instance after this change:
> 
> jdk.CPUInformation {
>   startTime = 05:28:24.506
>   cpu = "AArch64"
>   description = "AArch64 a1.2xlarge  0x41:0x0:0xd08:3, simd, crc, aes, sha1, sha256"
>   sockets = 8
>   cores = 8
>   hwThreads = 8
> }

Yasumasa Suenaga has updated the pull request incrementally with one additional commit since the last revision:

  check the contents whether it is just "\n"

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3259/files
  - new: https://git.openjdk.java.net/jdk/pull/3259/files/e5b75dc5..a1b94754

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3259&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3259&range=02-03

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3259.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3259/head:pull/3259

PR: https://git.openjdk.java.net/jdk/pull/3259