Update kernel API header to include link_layer

Update kernel API header to include link_layer

Modify the code to handle returning the link layer of a port from the
kernel to the library.  The kernel has done this since commit
2420b60b1dc4 ("IB/uverbs: Return link layer type to userspace for
query port operation"), merged in 2.6.37-rc1.

The new field does not change the size of struct ibv_query_port_resp
as it replaces a reserved field.  Binary compatibility between the
kernel to the library is kept, since old kernels running below new
library will not zero that field, so it will be read as "unspecified,"
while an old library running over new kernel will ignore the value
returned by the kernel.

The solution was suggested by Roland Dreier <roland@purestorage.com>
and Jason Gunthorpe <jgunthorpe@obsidianresearch.com>

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.co.il>
Signed-off-by: Eli Cohen <eli@mellanox.co.il>