[arm] Fix vmov immediate for ARMv6.

[arm] Fix vmov immediate for ARMv6.

vmov immediate was always emitting movt for some immediates wether or
not the CPU supported ARMv7.

BUG=v8:4019
LOG=n

Committed: https://crrev.com/81703350bbb9923d211fe5b79e90bd458b0916e2
Cr-Commit-Position: refs/heads/master@{#28691}

[Rodolph Perfetta (ARM), 2015-05-28 18:10:37]

rodolph.perfetta@arm.com changed reviewers:
+ bmeurer@chromium.org, ulan@chromium.org

[Benedikt Meurer, 2015-05-29 05:06:37]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-05-29 05:06:38]

lgtm

[commit-bot: I haz the power, 2015-05-29 05:06:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1160093002/1

[commit-bot: I haz the power, 2015-05-29 05:31:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-29 05:31:51]

Patchset 1 (id:??) landed as
https://crrev.com/81703350bbb9923d211fe5b79e90bd458b0916e2
Cr-Commit-Position: refs/heads/master@{#28691}