README: add more information about passing arguments to uinit command
README: add more information about passing arguments to uinit command

Signed-off-by: Jens Drenhaus <0fc5ffcb4f0b11dec7b85a2f9a1d8a2e56c0aebf@9elements.com>

u-root/u-root,u-root/u-root,u-root/u-root