anv: rename the vm_bind vfuncs

anv: rename the vm_bind vfuncs

The only driver that has a vm_bind ioctl is xe.ko, and its vm_bind
ioctl is not called GEM vm_bind, it's just DRM_IOCTL_XE_VM_BIND
(without GEM anywhere). Back when i915.ko was going to have a vm_bind
ioctl it had GEM on its name, so I guess that's how "gem" appeared in
the naming here, but now nothing does, so let's get rid of it.

Also, these vfuncs we have are specifically made to bind and unbind
whole BOs, so rename them to vm_bind_bo() and vm_unbind_bo() in order
to try to clarify what they mean. The goal is to add a more generic
vm_bind() later that can do anything.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24681>