drm/panic: Better binary encoding in QR code

drm/panic: Better binary encoding in QR code

The current encoding, is done by converting 13bits of input into 4
decimal digits, that are then encoded efficiently using the numeric
encoding of the QR code specification.
The Fido v2.2 specification [1] uses a similar approach for its
QR-initiated authentication. The only difference is that it converts
7 bytes (56bits) of input into 17 decimal digits. The benefit is that
the algorithm doesn't require to split input bytes into 13bits chunk,
and the ratio is a bit better.
This improvement was proposed by Jó Ágila Bitsch in [2].
drm_panic is still young, and the QR code feature is not widely used,
so it's still time to switch to a common algorithm, shared with a
widely used standard.
I also changed the name of the url parameter, from zl= to z=, so the
website can keep backward compatibility if needed.

[1] https://fidoalliance.org/specs/fido-v2.2-rd-20230321/fido-client-to-authenticator-protocol-v2.2-rd-20230321.html#hybrid-qr-initiated
[2] https://github.com/kdj0c/panic_report/issues/2

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250128165254.893204-1-jfalempe@redhat.com