Documentation/locking/locktypes: Fix local_locks documentation

Fix issues with local_locks documentation:

 - fix function names, local_lock.h has local_unlock_irqrestore(), not
   local_lock_irqrestore()

 - fix mapping table, local_unlock_irqrestore() maps to
   local_irq_restore(), not _save()

Signed-off-by: Marta Rybczynska <rybczynska@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/CAApg2=SKxQ3Sqwj6TZnV-0x0cKLXFKDaPvXT4N15MPDMKq724g@mail.gmail.com