tools: dumpimage: Remove remaining mentions of the -i option

The -i option of the dumpimage tool has been removed so it should no
longer be documented in the README file. Refer readers to the tool's
help output rather than maintain a copy of the usage in the README.

Finally, adjust the example dumpfile invocation in imagetool.h to use
the -o option instead of the removed -i option.

Fixes: 12b831879a ("tools: dumpimage: Simplify arguments")
Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Martyn Welch <martyn.welch@collabora.com>
Acked-by: Martyn Welch <martyn.welch@collabora.com>

README

@@ -3832,16 +3832,8 @@ when your kernel is intended to use an initial ramdisk:
 	Load Address: 0x00000000
 	Entry Point:  0x00000000
 
-The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
-option performs the converse operation of the mkimage's second form (the "-d"
-option). Given an image built by mkimage, the dumpimage extracts a "data file"
-from the image:
-
-	tools/dumpimage -i image -T type -p position data_file
-	  -i ==> extract from the 'image' a specific 'data_file'
-	  -T ==> set image type to 'type'
-	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
-
+The "dumpimage" tool can be used to disassemble or list the contents of images
+built by mkimage. See dumpimage's help output (-h) for details.
 
 Installing a Linux Image:
 -------------------------

tools/imagetool.h

@@ -126,9 +126,9 @@ struct image_type_params {
 					struct image_tool_params *);
 	/*
 	 * This function is used by the command to retrieve a component
-	 * (sub-image) from the image (i.e. dumpimage -i <image> -p <position>
-	 * <sub-image-name>).
-	 * Thus the code to extract a file from an image must be put here.
+	 * (sub-image) from the image (i.e. dumpimage -p <position>
+	 * -o <component-outfile> <image>). Thus the code to extract a file
+	 * from an image must be put here.
 	 *
 	 * Returns 0 if the file was successfully retrieved from the image,
 	 * or a negative value on error.