Implement PTE for RiscV

[Esgr0bar]

impl PageTableEntryTrait for PageTableEntry {
    type Address = u64;
    type Flags = u64;

    // FIXME: Implement the following methods
    fn is_dirty(&self) -> bool {
        todo!()
    }

    fn is_accessed(&self) -> bool {
        todo!()
    }

    fn is_global(&self) -> bool {
        todo!()
    }

    fn is_readable(&self) -> bool {
        todo!()
    }

    fn is_writable(&self) -> bool {
        todo!()
    }

    fn is_executable(&self) -> bool {
        todo!()
    }
}```

[theo-abel]

Should be good with #15

[theo-abel]

PR merged