[WAN]: Remove broken and unmaintained Sangoma drivers.

The in-kernel Sangoma drivers are both not compiling and marked as BROKEN
since at least kernel 2.6.0.

Sangoma offers out-of-tree drivers, and David Mandelstam told me Sangoma
does no longer maintain the in-kernel drivers and prefers to provide them
as a separate installation package.

This patch therefore removes these drivers.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>