net: rds: Remove repeated function names from debug output

The macro rdsdebug is defined as

  pr_debug("%s(): " fmt, __func__ , ##args)

Hence it doesn't make sense to include the name of the calling
function explicitly in the format string passed to rdsdebug.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>