tools: kwbimage: Remove unused parameter

The parameter 'params' of the image_headersz_v1 function is never used
by the function.

Hence, remove it.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>