gianfar: Fix build with CONFIG_NET_POLL_CONTROLLER=y

commit 46ceb60c ("gianfar: Add
Multiple group Support") introduced the following build error
with CONFIG_NET_POLL_CONTROLLER=y:

  CC      ggianfar.o
ggianfar.c: In function 'gfar_netpoll':
ggianfar.c:2653: error: invalid storage class for function 'gfar_interrupt'
ggianfar.c:2652: warning: ISO C90 forbids mixed declarations and code
ggianfar.c:2681: error: invalid storage class for function 'adjust_link'
ggianfar.c:2764: error: invalid storage class for function 'gfar_set_multi'
ggianfar.c:2855: error: invalid storage class for function 'gfar_clear_exact_match'
ggianfar.c:2877: error: invalid storage class for function 'gfar_set_hash_for_addr'
ggianfar.c:2898: error: invalid storage class for function 'gfar_set_mac_for_addr'
ggianfar.c:2922: error: invalid storage class for function 'gfar_error'
ggianfar.c:3020: warning: ISO C90 forbids mixed declarations and code
ggianfar.c:3032: error: invalid storage class for function 'gfar_init'
ggianfar.c:3037: error: invalid storage class for function 'gfar_exit'
ggianfar.c:3041: error: initializer element is not constant
ggianfar.c:3042: error: initializer element is not constant
ggianfar.c:3042: warning: ISO C90 forbids mixed declarations and code
ggianfar.c:3042: error: expected declaration or statement at end of input
make[1]: *** [ggianfar.o] Error 1

This patch fixes the issue.

Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>