chore: remove useless conversion in fdt.rs

After changing the type of `MMIODeviceInfo::irq` from
`Option<NonZeroU32>` to `Option<u32>`, we don't need to convert
NonZeroU32 to u32 with .into() anymore. Thus any occurance is removed.

Signed-off-by: Sheng-Wei (Way) Chen <[email protected]>

Author: Swchexit

src/vmm/src/arch/aarch64/fdt.rs

@@ -362,7 +362,7 @@ fn create_virtio_node(fdt: &mut FdtWriter, dev_info: &MMIODeviceInfo) -> Result<
         "interrupts",
         &[
             GIC_FDT_IRQ_TYPE_SPI,
-            dev_info.irq.unwrap().into(),
+            dev_info.irq.unwrap(),
             IRQ_TYPE_EDGE_RISING,
         ],
     )?;
@@ -383,7 +383,7 @@ fn create_serial_node(fdt: &mut FdtWriter, dev_info: &MMIODeviceInfo) -> Result<
         "interrupts",
         &[
             GIC_FDT_IRQ_TYPE_SPI,
-            dev_info.irq.unwrap().into(),
+            dev_info.irq.unwrap(),
             IRQ_TYPE_EDGE_RISING,
         ],
     )?;