qlcnic: Add support to enable capability to extend minidump for iSCSI

In some cases it is required to capture minidump for iSCSI functions
as part of default minidump collection process. To enable this, firmware
exports it's capability and driver need to enable that capability
by issuing a mailbox command.

With this feature, firmware can provide additional iSCSI function's
minidump with smaller minidump capture mask (0x1f).

Signed-off-by: Shahed Shaikh <shahed.shaikh@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>