Fix long latency in MHI PM sys error transition

[Qingtao Cao]

Hi community,

I have been using and testing an older kernel than the latest and found that
once the fix to mhi_pm_disable_transition() is brought forward to
mhi_pm_sys_error_transition() to poll if the hardware may have cleared the
RESET bit in its MHI control register, the handling of AT!RESET command on
my EM9291 cellular modem won't have to wait 24 seconds (but 11 seconds or so)
to finish.

Please kindly review this change, thanks!

Regards,
Qingtao