um: convert irq_lock to raw spinlock

Since this is deep in the architecture, and the code is
called nested into other deep management code, this really
needs to be a raw spinlock. Convert it.

Link: https://patch.msgid.link/20250110125550.32479-8-johannes@sipsolutions.net


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>