drivers/net/s2io.c section fixes

Code used by the non-__devinit s2io_open() mustn't be __devinit.

This patch fixes the following section mismatch with CONFIG_HOTPLUG=n:

<--  snip  -->

...
WARNING: vmlinux.o(.text+0x6f6e3e): Section mismatch: reference to .init.text.20:s2io_test_intr (between 's2io_open' and 's2io_ethtool_sset')
...

<--  snip  -->

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>