Revert "MIPS: Delete unused function add_temporary_entry."

This reverts commit d7a887a73d.

Function add_temporary_entry is needed by bcm47xx to support highmem. We
need to add a temporary entry to check for amount of RAM.
The only change made in this revert was replacing (ENTER|EXIT)_CRITICAL.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/7395/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/pgtable-32.h

@@ -18,6 +18,16 @@
 
 #include <asm-generic/pgtable-nopmd.h>
 
+/*
+ * - add_temporary_entry() add a temporary TLB entry. We use TLB entries
+ *	starting at the top and working down. This is for populating the
+ *	TLB before trap_init() puts the TLB miss handler in place. It
+ *	should be used only for entries matching the actual page tables,
+ *	to prevent inconsistencies.
+ */
+extern int add_temporary_entry(unsigned long entrylo0, unsigned long entrylo1,
+			       unsigned long entryhi, unsigned long pagemask);
+
 /*
  * Basically we have the same two-level (which is the logical three level
  * Linux page table layout folded) page tables as the i386.  Some day