scripts: zephyr_flash_debug: fix Nios II comment

Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
diff --git a/scripts/support/zephyr_flash_debug.py b/scripts/support/zephyr_flash_debug.py
index 2c463aa..cc1480e 100755
--- a/scripts/support/zephyr_flash_debug.py
+++ b/scripts/support/zephyr_flash_debug.py
@@ -547,7 +547,7 @@
         Required:
 
         - O: build output directory
-        - KERNEL_HEX_NAME: name of kernel binary in ELF format
+        - KERNEL_HEX_NAME: name of kernel binary in HEX format
         - NIOS2_CPU_SOF: location of the CPU .sof data
         - ZEPHYR_BASE: zephyr Git repository base directory
         '''