anvl: Clean up install script a bit

- add check_options function
- use rootfs_file instead of just file for the rootfs to avoid confusion
- renumber exit codes to start from 1 for each function
- untangle pad_image function that accidentally got nested into update_function
- add error checks for calling the functions

Signed-off-by: Tony Lindgren <tony@atomide.com>
anvl: Fix getopt quotes by calling eval properly

Otherwise quoted strings won't get properly handled.

Signed-off-by: Tony Lindgren <tony@atomide.com>
anvl: Add support for partitioning, formatting and untarring the rootfs

Only do it if rootfs.tar.gz file is specified.

Signed-off-by: Tony Lindgren <tony@atomide.com>