drm: adp: Remove pointless irq_lock spin lock

Interrupt handlers run with interrupts disabled so it is not necessary
to protect them against reentrancy.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Janne Grunau <j@jannau.net>
Link: https://lore.kernel.org/r/20250428-drm_adp_fixes-v2-4-912e081e55d8@jannau.net


Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>