net: bridge: make struct opening bracket consistent

Currently we have a mix of opening brackets on new lines and on the same
line, let's move them all on the same line.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>