drm/panic: correctly indent continuation of line in list item

It is common practice in Rust to indent the next line the same amount of
space as the previous one if both belong to the same list item. Clippy
checks for this with the lint `doc_lazy_continuation`.

    error: doc list item without indentation
    --> drivers/gpu/drm/drm_panic_qr.rs:979:5
        |
    979 | /// conversion to numeric segments.
        |     ^
        |
        = help: if this is supposed to be its own paragraph, add a blank line
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_lazy_continuation


        = note: `-D clippy::doc-lazy-continuation` implied by `-D warnings`
        = help: to override `-D warnings` add `#[allow(clippy::doc_lazy_continuation)]`
    help: indent this line
        |
    979 | ///   conversion to numeric segments.
        |     ++

Indent the offending line by 2 more spaces to remove this Clippy error.

Fixes: cb5164ac ("drm/panic: Add a QR code panic screen")
Reported-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/Rust-for-Linux/linux/issues/1123


Signed-off-by: Thomas Böhler <witcher@wiredspace.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20241019084048.22336-6-witcher@wiredspace.de


[ Reworded to indent Clippy's message. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>