mkimage: update man page and -h output

The man page correctly said that -B was ignored without -E, while the
`mkimage -h` output suggested otherwise. Now that -B can actually be
used by itself, update the man page.

While at it, also amend the `mkimage -h` line to mention the
connection with -E.

The FDT header is a fixed 40 bytes, so its size cannot (and is not)
modified, while its alignment is a property of the address in RAM one
loads the FIT to, so not something mkimage can affect in any way. (In
the file itself, the header is of course at offset 0, which has all
possible alignments already.)

Reported-by: Sean Anderson <seanga2@gmail.com>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>

doc/mkimage.1

@@ -281,8 +281,10 @@ properties.  A \(oqdata-offset\(cq of 0 indicates that it starts in the first
 .BI \-B " alignment"
 .TQ
 .BI \-\-alignment " alignment"
-The alignment, in hexadecimal, that external data will be aligned to. This
-option only has an effect when \-E is specified.
+The alignment, in hexadecimal, that the FDT structure will be aligned
+to. With
+.BR \-E ,
+also specifies the alignment for the external data.
 .
 .TP
 .BI \-p " external-position"

tools/mkimage.c

@@ -112,7 +112,7 @@ static void usage(const char *msg)
 		"          -f => input filename for FIT source\n"
 		"          -i => input filename for ramdisk file\n"
 		"          -E => place data outside of the FIT structure\n"
-		"          -B => align size in hex for FIT structure and header\n"
+		"          -B => align size in hex for FIT structure and, with -E, for the external data\n"
 		"          -b => append the device tree binary to the FIT\n"
 		"          -t => update the timestamp in the FIT\n");
 #ifdef CONFIG_FIT_SIGNATURE