m68k/sun3: Kill pte_unmap() warnings

Since commit 31c91132 ("mm: check the argument
of kunmap on architectures without highmem"), we get lots of warnings like

arch/m68k/kernel/sys_m68k.c:508: warning: passing argument 1 of ‘kunmap’ from incompatible pointer type

As m68k doesn't support highmem anyway, open code the calls to kmap() and
kunmap() (the latter is a no-op) to kill the warnings, like is done on most
other architectures without CONFIG_HIGHPTE.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Sam Creasey <sammy@sammy.net>

arch/m68k/include/asm/sun3_pgtable.h

@@ -217,9 +217,8 @@ static inline pte_t pgoff_to_pte(unsigned off)
 /* Find an entry in the third-level pagetable. */
 #define pte_index(address) ((address >> PAGE_SHIFT) & (PTRS_PER_PTE-1))
 #define pte_offset_kernel(pmd, address) ((pte_t *) __pmd_page(*pmd) + pte_index(address))
-/* FIXME: should we bother with kmap() here? */
-#define pte_offset_map(pmd, address) ((pte_t *)kmap(pmd_page(*pmd)) + pte_index(address))
-#define pte_unmap(pte) kunmap(pte)
+#define pte_offset_map(pmd, address) ((pte_t *)page_address(pmd_page(*pmd)) + pte_index(address))
+#define pte_unmap(pte) do { } while (0)
 
 /* Macros to (de)construct the fake PTEs representing swap pages. */
 #define __swp_type(x)		((x).val & 0x7F)