parisc: Drop pa_swapper_pg_lock spinlock

This spinlock was dropped with commit b7795074 ("parisc: Optimize
per-pagetable spinlocks") in kernel v5.12.

Remove it to silence a sparse warning.
Signed-off-by: NHelge Deller <deller@gmx.de>
Reported-by: Nkernel test robot <lkp@intel.com>
Cc: <stable@vger.kernel.org> # v5.12+

arch/parisc/kernel/cache.c

@@ -50,9 +50,6 @@ void flush_instruction_cache_local(void); /* flushes local code-cache only */
  */
 DEFINE_SPINLOCK(pa_tlb_flush_lock);
 
-/* Swapper page setup lock. */
-DEFINE_SPINLOCK(pa_swapper_pg_lock);
-
 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
 int pa_serialize_tlb_flushes __ro_after_init;
 #endif