click.cc: Update initrd structure members

click.cc: Update initrd structure members

Update initrd structures to match the updates to the Unikraft core.
Use `pbase` instead of `base`, and pass a `struct ukplat_memregion desc **`
to the `find_initrd` function.

Signed-off-by: Stefan Jumarea <stefanjumarea02@gmail.com>
Reviewed-by: Razvan Deaconescu <razvand@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #7