Remove unneeded assertion

assert_VGPU_type_allowed now calls assert_VGPU_type_enabled

Signed-off-by: John Else <john.else@citrix.com>
Make free PCI functions check a bit more cautious

Signed-off-by: John Else <john.else@citrix.com>
Add API call PGPU.set_enabled_VGPU_types

Signed-off-by: John Else <john.else@citrix.com>
Make PGPU.enabled_VGPU_types settable on the CLI

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #1426 from johnelse/pgpu-fixes

A few fixes for dealing with PGPUs