net: rose: Fix fall-through warnings for Clang

[ Upstream commit 90d181ca ]

In preparation to enable -Wimplicit-fallthrough for Clang, fix multiple
warnings by explicitly adding multiple break statements instead of
letting the code fall through to the next case.

Link: https://github.com/KSPP/linux/issues/115


Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 34a500ca ("rose: fix dangling neighbour pointers in rose_rt_device_down()")
Signed-off-by: Sasha Levin <sashal@kernel.org>