fsl_ifc: fix typo in the NOR CSOR register definition

fsl_ifc: fix typo in the NOR CSOR register definition

The name of the define must indicate 'Asynchronous', so 'ASYNC' is more
appropriate. AYSNC is probably a typo, and checkpatch script is throwing
a warning if this is set in the board include files.

It is save to change this now as none of the existing designs is using it
so far, but we will use it in our design it help to make IFC settings
more transparent.

Signed-off-by: Aleksandar Gerasimovski <aleksandar.gerasimovski@hitachi-powergrids.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>