Fix ProtocolsPerHandle internal slice property.

[AtsukiTak]

The old implementation contains a protocols slice with a lifetime a.

pub struct ProtocolsPerHandle<'a> {
    boot_services: &'a BootServices,
    protocols: &'a mut [&'a Guid],
}

But protocols slice does not live long enough for 'a. It will be freed when the ProtocolsPerHandle struct is dropped.

From std doc, ( https://doc.rust-lang.org/nightly/core/slice/fn.from_raw_parts.html )

pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T]

The memory referenced by the returned slice must not be mutated for the duration of lifetime 'a.

The current codebase does not use this internal property except the protocols getter method. So having an invalid lifetime does not immediately cause undefined behavior but it is safer to fix.

Since I'm not a native English speaker, it is very appreciated to fix my English document :)

Thanks!

[nicholasbishop]

Looks good, thanks for the fix!