[arm] Fix detection of architecture versions.

[arm] Fix detection of architecture versions.

Use __ARM_ARCH_6ZK__ instead of __ARM_ARCH_6KZ__. The architecture is
technically called ARMv6KZ, but GCC has always called it 6ZK.

Clang defines __ARM_ARCH_6K__ for this target, and is unaffected.

BUG=v8:3978
LOG=N

Committed: https://crrev.com/84b9afe46695043d9d028a0a328f59159a10cbef
Cr-Commit-Position: refs/heads/master@{#28709}

[jbramley, 2015-05-29 16:00:00]

jacob.bramley@arm.com changed reviewers:
+ bmeurer@chromium.org, ulan@chromium.org

[Benedikt Meurer, 2015-06-01 03:58:15]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-06-01 03:58:15]

lgtm

[commit-bot: I haz the power, 2015-06-01 03:58:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1145973004/1

[commit-bot: I haz the power, 2015-06-01 04:26:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-01 04:26:40]

Patchset 1 (id:??) landed as
https://crrev.com/84b9afe46695043d9d028a0a328f59159a10cbef
Cr-Commit-Position: refs/heads/master@{#28709}