drivers/net/wireless: fix sparse warnings: symbol shadows an earlier one

Impact:
  Move variable closer to usage resp.
  remove redundant variables resp.
  rename function scope variable.

Fix this sparse warnings:
  drivers/net/wireless/airo.c:3840:29: warning: symbol 'i' shadows an earlier one
  drivers/net/wireless/airo.c:3751:13: originally declared here
  drivers/net/wireless/airo.c:3847:29: warning: symbol 'i' shadows an earlier one
  drivers/net/wireless/airo.c:3751:13: originally declared here
  drivers/net/wireless/airo.c:3861:21: warning: symbol 'i' shadows an earlier one
  drivers/net/wireless/airo.c:3751:13: originally declared here
  drivers/net/wireless/wavelan.c:43:13: warning: symbol 'irq' shadows an earlier one
  drivers/net/wireless/wavelan.p.h:692:17: originally declared here

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