Infrastructure to support verbs extensions

Infrastructure to support verbs extensions

Infrastructure to support extended verbs capabilities in a forward/backward
manner.

The general operation as shown in the following pseudo-code:

ibv_open_device()
{
	context = device->ops.alloc_context();
	if (context == -1) {
		context_ex = malloc(verbs_context + verbs_device->context_size);
		verbs_device->init_context(context_ex);
		context_ex->context.abi_compat = -1;
	}
}

If the underlying provider supports extensions, it returns -1 from its
alloc_context() call.  Ibverbs then allocates the ibv_context structure and
calls into the provider to finish initializing it.

When extensions are supported, the ibv_device structure is embedded in a
larger verbs_device structure.  Similarly, ibv_context is embedded inside
a larger verbs_context structure.

Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Tzahi Oved <tzahio@mellanox.com>