udp: Neaten function pointer calls and add braces

Standardize function pointer uses.

Convert calling style from:
	(*foo)(args...);
to:
	foo(args...);

Other miscellanea:

o Add braces around loops with single ifs on multiple lines
o Realign arguments around these functions
o Invert logic in if to return immediately.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>