parisc: Drop PMD_SHIFT from calculation in pgtable.h

PMD_SHIFT isn't defined if CONFIG_PGTABLE_LEVELS == 3, and as
such the kernel test robot found this warning:

 In file included from include/linux/pgtable.h:6,
                  from arch/parisc/kernel/head.S:23:
 arch/parisc/include/asm/pgtable.h:169:32: warning: "PMD_SHIFT" is not defined, evaluates to 0 [-Wundef]
     169 | #if (KERNEL_INITIAL_ORDER) >= (PMD_SHIFT)

Avoid the warning by using PLD_SHIFT and BITS_PER_PTE.
Signed-off-by: Helge Deller <deller@gmx.de>
Reported-by: kernel test robot <lkp@intel.com>
Cc: <stable@vger.kernel.org> # 6.0+

arch/parisc/include/asm/pgtable.h

@@ -166,8 +166,8 @@ extern void __update_cache(pte_t pte);
 
 /* This calculates the number of initial pages we need for the initial
  * page tables */
-#if (KERNEL_INITIAL_ORDER) >= (PMD_SHIFT)
-# define PT_INITIAL	(1 << (KERNEL_INITIAL_ORDER - PMD_SHIFT))
+#if (KERNEL_INITIAL_ORDER) >= (PLD_SHIFT + BITS_PER_PTE)
+# define PT_INITIAL	(1 << (KERNEL_INITIAL_ORDER - PLD_SHIFT - BITS_PER_PTE))
 #else
 # define PT_INITIAL	(1)  /* all initial PTEs fit into one page */
 #endif