imx8mq_evk/README: fix DDR training firmware path

Remove a redundant directory level.

Reported-by: Ofer Heifetz <ofer.heifetz@valens.com>
Tested-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
1 file changed