drivers: intc: plic: print ISR(ARG) in shell cmd

Print the ISR & its ARG along with the IRQ and Hits in
`plic stats get <intc>` command, i.e.

```CONFIG_SYMTAB=n
uart:~$ plic stats get interrupt-controller@c000000
   IRQ        Hits	ISR(ARG)
    10         541	0x800054ee(0x80008170)
```

```CONFIG_SYMTAB=y
uart:~$ plic stats get interrupt-controller@c000000
   IRQ        Hits	ISR(ARG)
    10         114	uart_ns16550_isr(0x80008230)
```

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
Signed-off-by: Yong Cong Sin <yongcong.sin@gmail.com>