debian/control: remove arm64 dkms recommends

debian/control: remove arm64 dkms recommends

This was meant when arm64 absolutely required the dkms modules to work.
But there are platforms which can work without now.

We already have a arch neutral suggests, so no need to replace this.

Given the complexity dkms sometimes brings on e.g. kernel updates
dropping the recommends helps more systems (by avoiding those issues)
than it hurts (by users of those needing it installing the dkms
packages)

Change-Id: I99a060092d685a8cb87db6d0259e4ab18a823d7e
Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>