Instead of just printing a warning that an image is too big, also
print both actual size and limit in the string:
WARNING: Image file somename.bin is too big: 2096101 > 1048576
Since the kernel size is checked via the same function (if
KERNEL_SIZE is specified), this will also apply to the kernel
image size check.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>