ibmvnic: Don't handle RX interrupts when not up.

ibmvnic: Don't handle RX interrupts when not up.

Initiating a kdump via the command line can cause a pending interrupt
to be handled by the ibmvnic driver when initializing the sub-CRQ
irqs during driver initialization.

NIP [d000000000ca34f0] ibmvnic_interrupt_rx+0x40/0xd0 [ibmvnic]
LR [c000000008132ef0] __handle_irq_event_percpu+0xa0/0x2f0
Call Trace:
[c000000047fcfde0] [c000000008132ef0] __handle_irq_event_percpu+0xa0/0x2f0
[c000000047fcfea0] [c00000000813317c] handle_irq_event_percpu+0x3c/0x90
[c000000047fcfee0] [c00000000813323c] handle_irq_event+0x6c/0xd0
[c000000047fcff10] [c0000000081385e0] handle_fasteoi_irq+0xf0/0x250
[c000000047fcff40] [c0000000081320a0] generic_handle_irq+0x50/0x80
[c000000047fcff60] [c000000008014984] __do_irq+0x84/0x1d0
[c000000047fcff90] [c000000008027564] call_do_irq+0x14/0x24
[c00000003c92af00] [c000000008014b70] do_IRQ+0xa0/0x120
[c00000003c92af50] [c000000008002594] hardware_interrupt_common+0x114/0x180

Signed-off-by: David S. Miller <davem@davemloft.net>