smsc911x: fix mac_lock acquision before calling smsc911x_mac_read

smsc911x: fix mac_lock acquision before calling smsc911x_mac_read

When SMSC911X_SAVE_MAC_ADDRESS flag is enabled the driver calls
smsc911x_mac_read and smsc911x_mac_read function without acquiring mac_lock
spinlock

This patch fixes following warning

smsc911x: Driver version 2008-10-21.
------------[ cut here ]------------
WARNING: at drivers/net/smsc911x.c:261 smsc911x_mac_read+0x24/0x220()
Modules linked in:
[<c0060858>] (unwind_backtrace+0x0/0xe0) from [<c009322c>] (warn_slowpath_common+0x4c/0x64)
[<c009322c>] (warn_slowpath_common+0x4c/0x64) from [<c009325c>] (warn_slowpath_null+0x18/0x1c)
[<c009325c>] (warn_slowpath_null+0x18/0x1c) from [<c0324bec>] (smsc911x_mac_read+0x24/0x220)
[<c0324bec>] (smsc911x_mac_read+0x24/0x220) from [<c0434788>] (smsc911x_read_mac_address+0x18/0x6c)
[<c0434788>] (smsc911x_read_mac_address+0x18/0x6c) from [<c0434c74>] (smsc911x_drv_probe+0x498/0x1788)
[<c0434c74>] (smsc911x_drv_probe+0x498/0x1788) from [<c02d3e54>] (platform_drv_probe+0x14/0x18)
[<c02d3e54>] (platform_drv_probe+0x14/0x18) from [<c02d2d60>] (driver_probe_device+0xc8/0x184)
[<c02d2d60>] (driver_probe_device+0xc8/0x184) from [<c02d2e84>] (__driver_attach+0x68/0x8c)
[<c02d2e84>] (__driver_attach+0x68/0x8c) from [<c02d1fc8>] (bus_for_each_dev+0x48/0x74)
[<c02d1fc8>] (bus_for_each_dev+0x48/0x74) from [<c02d2660>] (bus_add_driver+0x9c/0x228)
[<c02d2660>] (bus_add_driver+0x9c/0x228) from [<c02d3598>] (driver_register+0xa0/0x124)
[<c02d3598>] (driver_register+0xa0/0x124) from [<c0050668>] (do_one_initcall+0x94/0x168)
[<c0050668>] (do_one_initcall+0x94/0x168) from [<c0008984>] (kernel_init+0xa0/0x154)
[<c0008984>] (kernel_init+0xa0/0x154) from [<c005afac>] (kernel_thread_exit+0x0/0x8)
---[ end trace 2c931a35b7885770 ]---

Signed-off-by: Enric Balletbo i Serra <eballetbo@iseebcn.com>
Signed-off-by: David S. Miller <davem@davemloft.net>