imx8mq_evk/README: fix DDR training firmware path

Remove a redundant directory level.
Reported-by: NOfer Heifetz <ofer.heifetz@valens.com>
Tested-by: NFabio Estevam <festevam@gmail.com>
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>
Reviewed-by: NPeng Fan <peng.fan@nxp.com>

board/freescale/imx8mq_evk/README

@@ -20,7 +20,7 @@ $ wget https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/firmware-imx-7.9.bin
 $ chmod +x firmware-imx-7.9.bin
 $ ./firmware-imx-7.9.bin
 $ cp firmware-imx-7.9/firmware/hdmi/cadence/signed_hdmi_imx8m.bin $(srctree)
-$ cp firmware-imx-7.9/firmware-imx-7.9/firmware/ddr/synopsys/lpddr4*.bin $(srctee)
+$ cp firmware-imx-7.9/firmware/ddr/synopsys/lpddr4*.bin $(srctee)
 
 Build U-Boot
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