update pico-serprog to new revision
    
    this merges the fix from:
    https://codeberg.org/libreboot/pico-serprog/pulls/1
    
    however, PRs are not to be sent there. riku merged it in
    his repository, and i pulled it in the mirror hosted
    on libreboot codeberg
    
    Signed-off-by: Leah Rowe <leah@libreboot.org>