Input: usbtouchscreen - refactor endpoint lookup

Input: usbtouchscreen - refactor endpoint lookup

Use the common USB helpers for looking up bulk and interrupt endpoints
(and determining endpoint numbers) instead of open coding.

Note that the NEXIO data interface has two bulk endpoints (see commit
5197424cdccc ("Input: usbtouchscreen - add NEXIO (or iNexio) support")
for the descriptors).

The lookup in probe handles both bulk-in and interrupt-in endpoints and
was added to handle NEXIO devices. Replace the open coded lookup with a
lookup for the common interrupt endpoint and an explicit fallback
accepting a bulk endpoint.

This iterates over the (two) endpoints twice for NEXIO devices but makes
it more clear what is going on.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20260401082212.2180434-1-johan@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>