Support create pvc in other regions

[RottenLeaf24]

/kind feature

What happened?
When I create pvc use aws-ebs-csi-driver,if the pvc in Tokyo region always get the error like:

could not create volume in EC2: InvalidZone.NotFound: The zone 'ap-northeast-1c' does not exist.
or
could not create volume in EC2: InvalidZone.NotFound: The zone 'ap-northeast-1a' does not exist.

The reason for this phenomenon is cause by multiple region.
After multiple tests, I can confirm the aws-ebs-csi-driver can only create pvc in the same region with controller.When the region of pvc and controller is different,the ebs-csi-node can report it's own zone to controller,but the controller can't recognize the zone in other region.Then we get the error:The zone does not exist.

What you expected to happen?
Can create cross-regional pvc in kubernetes cluster on aws machine by aws-ebs-csi-driver.
How to reproduce it (as minimally and precisely as possible)?
Create a cross-regional kubernetes cluster,and create a pvc in a different region with ebs-csi-controller pod.
Anything else we need to know?:

Environment

• Kubernetes version (use kubectl version):
  Client Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.3", GitCommit:"2d3c76f9091b6bec110a5e63777c332469e0cba2", GitTreeState:"clean", BuildDate:"2019-08-19T11:13:54Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"linux/amd64"}
  Server Version: version.Info{Major:"1", Minor:"15", GitVersion:"v1.15.3", GitCommit:"2d3c76f9091b6bec110a5e63777c332469e0cba2", GitTreeState:"clean", BuildDate:"2019-08-19T11:05:50Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"linux/amd64"}

• Driver version:
  latest alpha

[leakingtapan]

Yep. The current controller service assumes that PVC's are in the same region as the controller. This is definitely something I can improve. See here about how the cloud struct is initialized.

I would like to assign this as a feature. Please up vote if this feature is important to you.

/kind feature

[RottenLeaf24]

That's wonderful,this feature will bring us great convenience.And I think this feature will also bring a lot of benefits to other users who have cross-regional kubernetes cluster on aws.