Do not check if WTF_ARM_ARCH_VERSION is defined in WTF_ARM_ARCH_AT_LEAST macro
https://bugs.webkit.org/show_bug.cgi?id=114127

Reviewed by Benjamin Poulain.

Platform.h defines WTF_ARM_ARCH_VERSION for CPU(ARM) always and removing
the check works around a bug in older Microsoft compiler versions.

* wtf/Platform.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147881 268f45cc-cd09-0410-ab3c-d52691b4dbfc