mt76: mt7921: fix possible invalid register access

mt76: mt7921: fix possible invalid register access

Disable the interrupt and synchronze for the pending irq handlers to ensure
the irq tasklet is not being scheduled after the suspend to avoid the
possible invalid register access acts when the host pcie controller is
suspended.

[17932.910534] mt7921e 0000:01:00.0: pci_pm_suspend+0x0/0x22c returned 0 after 21375 usecs
[17932.910590] pcieport 0000:00:00.0: calling pci_pm_suspend+0x0/0x22c @ 18565, parent: pci0000:00
[17932.910602] pcieport 0000:00:00.0: pci_pm_suspend+0x0/0x22c returned 0 after 8 usecs
[17932.910671] mtk-pcie 11230000.pcie: calling platform_pm_suspend+0x0/0x60 @ 22783, parent: soc
[17932.910674] mtk-pcie 11230000.pcie: platform_pm_suspend+0x0/0x60 returned 0 after 0 usecs

...

17933.615352] x1 : 00000000000d4200 x0 : ffffff8269ca2300
[17933.620666] Call trace:
[17933.623127]  mt76_mmio_rr+0x28/0xf0 [mt76]
[17933.627234]  mt7921_rr+0x38/0x44 [mt7921e]
[17933.631339]  mt7921_irq_tasklet+0x54/0x1d8 [mt7921e]
[17933.636309]  tasklet_action_common+0x12c/0x16c
[17933.640754]  tasklet_action+0x24/0x2c
[17933.644418]  __do_softirq+0x16c/0x344
[17933.648082]  irq_exit+0xa8/0xac
[17933.651224]  scheduler_ipi+0xd4/0x148
[17933.654890]  handle_IPI+0x164/0x2d4
[17933.658379]  gic_handle_irq+0x140/0x178
[17933.662216]  el1_irq+0xb8/0x180
[17933.665361]  cpuidle_enter_state+0xf8/0x204
[17933.669544]  cpuidle_enter+0x38/0x4c
[17933.673122]  do_idle+0x1a4/0x2a8
[17933.676352]  cpu_startup_entry+0x24/0x28
[17933.680276]  rest_init+0xd4/0xe0
[17933.683508]  arch_call_rest_init+0x10/0x18
[17933.687606]  start_kernel+0x340/0x3b4
[17933.691279] Code: aa0003f5 d503201f f953eaa8 8b344108 (b9400113)
[17933.697373] ---[ end trace a24b8e26ffbda3c5 ]---
[17933.767846] Kernel panic - not syncing: Fatal exception in interrupt

Fixes: ffa1bf97425b ("mt76: mt7921: introduce PM support")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>