sfc: move channel alloc/removal code

Reallocation and copying code is included, as well as some housekeeping
code.
Other files have been patched up a bit to accommodate the changes.

Small code styling fixes included.

Signed-off-by: Alexandru-Mihai Maftei <amaftei@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>