z85230: fix warning in drivers/net/wan/z85230.c

this warning:

  drivers/net/wan/z85230.c: In function ‘z8530_interrupt’:
  drivers/net/wan/z85230.c:713: warning: ‘intr’ may be used uninitialized in this function

is clearly bogus - annotate it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: David S. Miller <davem@davemloft.net>