arm: mvebu: kwbimage: inline function to fix use-after-free

arm: mvebu: kwbimage: inline function to fix use-after-free

image_version_file()'s only use is to return the version number of the
specified image, and it's only called by kwbimage_generate().  This
version function mallocs "image_cfg" and reads the contents of the image
into that buffer.  Before return to its caller it frees the buffer.

After extracting the version, kwb_image_generate() tries to calculate
the header size by calling image_headersz_v1().  This function now
accesses "image_cfg", which has already been freed.

Since image_version_file() is only used by a single function, inline it
into kwbimage_generate() and only free the buffer after it is no longer
needed.  This also improves code readability since the code is mostly
equal to kwbimage_set_header().

Signed-off-by: Patrick Wildt <patrick@blueri.se>
Signed-off-by: Stefan Roese <sr@denx.de>