serial: 8250_port: Check IRQ data before use

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

serial: 8250_port: Check IRQ data before use

In case the leaf driver wants to use IRQ polling (irq = 0) and

IIR register shows that an interrupt happened in the 8250 hardware

the IRQ data can be NULL. In such a case we need to skip the wake

event as we came to this path from the timer interrupt and quite

likely system is already awake.

Without this fix we have got an Oops:

serial8250: ttyS0 at I/O 0x3f8 (irq = 0, base_baud = 115200) is a 16550A

...

BUG: kernel NULL pointer dereference, address: 0000000000000010

RIP: 0010:serial8250_handle_irq+0x7c/0x240

Call Trace:

? serial8250_handle_irq+0x7c/0x240

? __pfx_serial8250_timeout+0x10/0x10