net: replace macros net_random and net_srandom with direct calls to prandom

net: replace macros net_random and net_srandom with direct calls to prandom

This patch removes the net_random and net_srandom macros and replaces
them with direct calls to the prandom ones. As new commits only seem to
use prandom_u32 there is no use to keep them around.
This change makes it easier to grep for users of prandom_u32.

Signed-off-by: Aruna-Hewapathirane <[email protected]>
Suggested-by: Hannes Frederic Sowa <[email protected]>
Acked-by: Hannes Frederic Sowa <[email protected]>
Signed-off-by: David S. Miller <[email protected]>