net: rename random32 to prandom

Commit 496f2f93

 ("random32: rename random32 to prandom") renamed
random32() and srandom32() to prandom_u32() and prandom_seed()
respectively.

net_random() and net_srandom() need to be redefined with prandom_* in
order to finish the naming transition.

While I'm at it, enclose macro argument of net_srandom() with parenthesis.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>