locking/local_lock: Include missing headers

Including <linux/local_lock.h> into an empty TU will result in the
compiler complaining:

./include/linux/local_lock.h: In function ‘class_local_lock_irqsave_constructor’:
./include/linux/local_lock_internal.h:95:17: error: implicit declaration of function ‘local_irq_save’; <...>
   95 |                 local_irq_save(flags);                          \
      |                 ^~~~~~~~~~~~~~

As well as (some architectures only, such as 'sh'):

./include/linux/local_lock_internal.h: In function ‘local_lock_acquire’:
./include/linux/local_lock_internal.h:33:20: error: ‘current’ undeclared (first use in this function)
   33 |         l->owner = current;

Include missing headers to allow including local_lock.h where the
required headers are not otherwise included.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://patch.msgid.link/20251219154418.3592607-19-elver@google.com