drivers/net: fix sparse warnings: make do-while a compound statement

While at it insert some extra curly braces and fix formatting.

Fix this sparse warnings:

  drivers/net/atp.c:811:8: warning: do-while statement is not a compound statement
  drivers/net/atp.c:813:8: warning: do-while statement is not a compound statement
  drivers/net/atp.c:815:11: warning: do-while statement is not a compound statement
  drivers/net/atp.c:817:11: warning: do-while statement is not a compound statement
  drivers/net/plip.c:642:4: warning: do-while statement is not a compound statement
  drivers/net/plip.c:647:4: warning: do-while statement is not a compound statement
  drivers/net/plip.c:820:4: warning: do-while statement is not a compound statement
  drivers/net/plip.c:825:4: warning: do-while statement is not a compound statement
  drivers/net/starfire.c:886:3: warning: do-while statement is not a compound statement

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>