myri10ge: fix sleeping with bh disabled

napi_disable() can not be called with bh disabled, move locking just
around myri10ge_ss_lock_napi() .

Patches fixes following bug:

[  114.278378] BUG: sleeping function called from invalid context at net/core/dev.c:4383
<snip>
[  114.313712] Call Trace:
[  114.314943]  [<ffffffff817010ce>] dump_stack+0x19/0x1b
[  114.317673]  [<ffffffff810ce7f3>] __might_sleep+0x173/0x230
[  114.320566]  [<ffffffff815b3117>] napi_disable+0x27/0x90
[  114.323254]  [<ffffffffa01e437f>] myri10ge_close+0xbf/0x3f0 [myri10ge]

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Hyong-Youb Kim <hykim@myri.com>
Signed-off-by: David S. Miller <davem@davemloft.net>