IB/core: Fix comments of GID query functions

Exported symbol's comments should be with function definition and not in
the header file. Therefore comments of ib_find_cached_gid() and
ib_find_cached_gid_by_port() functions are moved closer to their
definitions.

The function name in then comment is different than the actual function
name, fix it to be same as ib_cache_gid_find_by_filter().

Also current comment section of ib_find_cached_gid_by_port() contains the
desciption of ib_find_cached_gid(), fix that as well.

Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>