The IMX serial driver is broken in the 4.9.x tree since 4.9.89.
Uwe's patch
6df765dca378bddf994cfd2044acafa501bd800f
please apply to clear the situation.
I know you very busy! -
It's best to email stable@xxxxxxxxxxxxxxx for stuff like this, as I
almost missed it...
Now queued up.
greg k-h