Currently the tool allows writing an invalid ROMFS image, with a bad header
or images smaller than minimum size, and only checks the image extension.
This commit allows deploying a ROMFS with either a ".img" or ".romfs"
extension (in the future support may be added for other extensions that
have different semantics, eg a manifest), and validates the image header
before writing.
Signed-off-by: iabdalkader <i.abdalkader@gmail.com>