qlcnic: Fix Kconfig dependency on HWMON

qlcnic: Fix Kconfig dependency on HWMON

Commit 1f0f467b670e "qlcnic: Add hwmon interface to export board
temperature" introduced a randconfig build error in the case
when the hwmon framework is built as a module and the qlcnic
driver itself is built-in:

drivers/built-in.o: In function `qlcnic_register_hwmon_dev':
drivers/net/ethernet/qlogic/qlcnic/qlcnic_sysfs.c:1301:
undefined reference to `hwmon_device_register_with_groups'
drivers/built-in.o: In function `qlcnic_unregister_hwmon_dev':
drivers/net/ethernet/qlogic/qlcnic/qlcnic_sysfs.c:1309:
undefined reference to `hwmon_device_unregister'.

This changes the Kconfig logic to enforce that the qlcnic hwmon
support can only be enabled if it is possible to successfully
build it.

Signed-off-by: Harish Patil <harish.patil@qlogic.com>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>