mips: Move __virt_addr_valid() to a place for MIPS 64

Commit d3ce8843 "MIPS: Fix modpost error in modules attepting to use
virt_addr_valid()" moved __virt_addr_valid() from a macro in a header
file to a function in ioremap.c. But ioremap.c is only compiled for MIPS
32, and not for MIPS 64.

When compiling for my yeeloong2, which supposedly supports hibernation,
which compiles kernel/power/snapshot.c which calls virt_addr_valid(), I
got this error:

  LD      init/built-in.o
kernel/built-in.o: In function `memory_bm_free':
snapshot.c:(.text+0x4c9c4): undefined reference to `__virt_addr_valid'
snapshot.c:(.text+0x4ca58): undefined reference to `__virt_addr_valid'
kernel/built-in.o: In function `snapshot_write_next':
(.text+0x4e44c): undefined reference to `__virt_addr_valid'
kernel/built-in.o: In function `snapshot_write_next':
(.text+0x4e890): undefined reference to `__virt_addr_valid'
make[1]: *** [vmlinux] Error 1
make: *** [sub-make] Error 2

I suspect that __virt_addr_valid() is fine for mips 64. I moved it to
mmap.c such that it gets compiled for mips 64 and 32.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/4842/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mm/ioremap.c

@@ -190,9 +190,3 @@ void __iounmap(const volatile void __iomem *addr)
 
 EXPORT_SYMBOL(__ioremap);
 EXPORT_SYMBOL(__iounmap);
-
-int __virt_addr_valid(const volatile void *kaddr)
-{
-	return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
-}
-EXPORT_SYMBOL_GPL(__virt_addr_valid);

arch/mips/mm/mmap.c

@@ -192,3 +192,9 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
 
 	return ret;
 }
+
+int __virt_addr_valid(const volatile void *kaddr)
+{
+	return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
+}
+EXPORT_SYMBOL_GPL(__virt_addr_valid);