tile: fix some -Wsign-compare warnings

Normally the build doesn't include these warnings, but at one
point I built with -Wsign-compare, and noticed a few things that
are technically bugs.  This change fixes those things.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

arch/tile/include/asm/io.h

@@ -255,7 +255,7 @@ static inline void writeq(u64 val, unsigned long addr)
 
 static inline void memset_io(volatile void *dst, int val, size_t len)
 {
-	int x;
+	size_t x;
 	BUG_ON((unsigned long)dst & 0x3);
 	val = (val & 0xff) * 0x01010101;
 	for (x = 0; x < len; x += 4)
@@ -265,7 +265,7 @@ static inline void memset_io(volatile void *dst, int val, size_t len)
 static inline void memcpy_fromio(void *dst, const volatile void __iomem *src,
 				 size_t len)
 {
-	int x;
+	size_t x;
 	BUG_ON((unsigned long)src & 0x3);
 	for (x = 0; x < len; x += 4)
 		*(u32 *)(dst + x) = readl(src + x);
@@ -274,7 +274,7 @@ static inline void memcpy_fromio(void *dst, const volatile void __iomem *src,
 static inline void memcpy_toio(volatile void __iomem *dst, const void *src,
 				size_t len)
 {
-	int x;
+	size_t x;
 	BUG_ON((unsigned long)dst & 0x3);
 	for (x = 0; x < len; x += 4)
 		writel(*(u32 *)(src + x), dst + x);

arch/tile/include/asm/mmzone.h

@@ -42,7 +42,7 @@ static inline int pfn_to_nid(unsigned long pfn)
 
 #define kern_addr_valid(kaddr)	virt_addr_valid((void *)kaddr)
 
-static inline int pfn_valid(int pfn)
+static inline int pfn_valid(unsigned long pfn)
 {
 	int nid = pfn_to_nid(pfn);
 

arch/tile/include/asm/spinlock_64.h

@@ -27,7 +27,7 @@
  * Return the "current" portion of a ticket lock value,
  * i.e. the number that currently owns the lock.
  */
-static inline int arch_spin_current(u32 val)
+static inline u32 arch_spin_current(u32 val)
 {
 	return val >> __ARCH_SPIN_CURRENT_SHIFT;
 }
@@ -36,7 +36,7 @@ static inline int arch_spin_current(u32 val)
  * Return the "next" portion of a ticket lock value,
  * i.e. the number that the next task to try to acquire the lock will get.
  */
-static inline int arch_spin_next(u32 val)
+static inline u32 arch_spin_next(u32 val)
 {
 	return val & __ARCH_SPIN_NEXT_MASK;
 }