imx: imx8mm_evk: spelling in readme file

Minor spelling fix in README file.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
diff --git a/board/freescale/imx8mm_evk/README b/board/freescale/imx8mm_evk/README
index 9921b35..fa3f079 100644
--- a/board/freescale/imx8mm_evk/README
+++ b/board/freescale/imx8mm_evk/README
@@ -3,7 +3,7 @@
 Quick Start
 ===========
 - Build the ARM Trusted firmware binary
-- Get ddr fimware
+- Get ddr firmware
 - Build U-Boot
 - Boot