mkimage: allow internalization of data-position

Make it possible for data that was externalized using a static external
position (-p) to be internalized. Enables the ability to convert
existing FIT images built with -p to be converted to a FIT image where the
data is internal, to be converted to a FIT image where the data is
external relative to the end of the FIT (-E) or change the initial
static external position to a different static external position (-p).

Removing the original external-data-related properties ensures that
they're not present after conversion. Without this, they would still be
present in the resulting FIT even if the FIT has been, for example,
internalized.

Signed-off-by: Lars Feyaerts <lars@bitbiz.be>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/mkimage.1 b/doc/mkimage.1
index 76c7859..d0a038a 100644
--- a/doc/mkimage.1
+++ b/doc/mkimage.1
@@ -860,6 +860,25 @@
 	\-K u\-boot.dtb -r kernel.itb
 .EE
 .RE
+.P
+Convert an existing FIT image from any of the three types of data storage
+(internal, external data-offset or external data-position) to another type
+of data storage.
+.RS
+.P
+.EX
+\fB// convert FIT from internal data to data-position
+\fBmkimage -p 0x20000 -F internal_data.itb
+.EE
+.EX
+\fB// convert FIT from data-position to data-offset
+\fBmkimage -E -F external_data-position.itb
+.EE
+.EX
+\fB// convert FIT from data-offset to internal data
+\fBmkimage -F external_data-offset.itb
+.EE
+.RE
 .
 .SH SEE ALSO
 .BR dtc (1),