net:sfc: fix non-freed irq in legacy irq mode

In the Linux kernel, the following vulnerability has been resolved:

net:sfc: fix non-freed irq in legacy irq mode

SFC driver can be configured via modparam to work using MSI-X, MSI or

legacy IRQ interrupts. In the last one, the interrupt was not properly

released on module remove.

It was not freed because the flag irqs_hooked was not set during

initialization in the case of using legacy IRQ.

Example of (trimmed) trace during module remove without this fix:

remove_proc_entry: removing non-empty directory 'irq/125', leaking at least '0000:3b:00.1'

WARNING: CPU: 39 PID: 3658 at fs/proc/generic.c:715 remove_proc_entry+0x15c/0x170

...trimmed...

Call Trace:

unregister_irq_proc+0xe3/0x100

free_desc+0x29/0x70

irq_free_descs+0x47/0x70

mp_unmap_irq+0x58/0x60

acpi_unregister_gsi_ioapic+0x2a/0x40

acpi_pci_irq_disable+0x78/0xb0

pci_disable_device+0xd1/0x100

efx_pci_remove+0xa1/0x1e0 [sfc]

pci_device_remove+0x38/0xa0

__device_release_driver+0x177/0x230

driver_detach+0xcb/0x110

bus_remove_driver+0x58/0xd0

pci_unregister_driver+0x2a/0xb0

efx_exit_module+0x24/0xf40 [sfc]

__do_sys_delete_module.constprop.0+0x171/0x280

? exit_to_user_mode_prepare+0x83/0x1d0

do_syscall_64+0x3d/0x80

entry_SYSCALL_64_after_hwframe+0x44/0xae

RIP: 0033:0x7f9f9385800b

...trimmed...