wifi: mt76: mt7921e: fix probe timeout after reboot

In system warm reboot scene, due to the polling timeout(now 1000us)
is too short to wait dma idle in time, it may make driver probe fail
with error code -ETIMEDOUT. Meanwhile, we also found the dma may take
around 70ms to enter idle state. Change the polling idle timeout to
100ms to avoid the probabilistic probe fail.

Tested pass with 5000 times warm reboot on x86 platform.

[4.477496] pci 0000:01:00.0: attach allowed to drvr mt7921e [internal device]
[4.478306] mt7921e 0000:01:00.0: ASIC revision: 79610010
[4.480063] mt7921e: probe of 0000:01:00.0 failed with error -110

Fixes: 0a1059d0 ("mt76: mt7921: move mt7921_dma_reset in dma.c")
Signed-off-by: Quan Zhou <quan.zhou@mediatek.com>
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>