i3c: dw: Initialize spinlock to avoid upsetting lockdep

i3c: dw: Initialize spinlock to avoid upsetting lockdep

The devs_lock spinlock introduced when adding support for ibi:s was
never initialized.

Fixes: e389b1d72a624 ("i3c: dw: Add support for in-band interrupts")
Suggested-by: Jani Nurminen <jani.nurminen@windriver.com>
Signed-off-by: Fredrik Markstrom <fredrik.markstrom@est.tech>
Reviewed-by: Ivar Holmqvist <ivar.holmqvist@est.tech>
Link: https://patch.msgid.link/20260116-i3c_dw_initialize_spinlock-v3-1-cf707b6ed75f@est.tech
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>