checkpatch: handle EXPORT_SYMBOL for DEVICE_ATTR and similar

Handly definitions similar to below.  The definition macro spits out a
symbol with a prefix.  Add matching of any identifier prefix:

    DEVICE_ATTR(link_power_management_policy, S_IRUGO | S_IWUSR,
            ata_scsi_lpm_show, ata_scsi_lpm_put);
    EXPORT_SYMBOL_GPL(dev_attr_link_power_management_policy);

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>