[XTENSA] Add volatile keyword to asm statements accessing counter registers

The compiler get's sometimes to smart and doesn't reread the
counter registers and the kernel doesn't schedule until the
counter wraps around.

Signed-off-by: Chris Zankel <chris@zankel.net>

include/asm-xtensa/timex.h

@@ -63,10 +63,10 @@ extern cycles_t cacheflush_time;
  * Register access.
  */
 
-#define WSR_CCOUNT(r)	  __asm__("wsr %0,"__stringify(CCOUNT) :: "a" (r))
-#define RSR_CCOUNT(r)	  __asm__("rsr %0,"__stringify(CCOUNT) : "=a" (r))
-#define WSR_CCOMPARE(x,r) __asm__("wsr %0,"__stringify(CCOMPARE)"+"__stringify(x) :: "a"(r))
-#define RSR_CCOMPARE(x,r) __asm__("rsr %0,"__stringify(CCOMPARE)"+"__stringify(x) : "=a"(r))
+#define WSR_CCOUNT(r)	  asm volatile ("wsr %0,"__stringify(CCOUNT) :: "a" (r))
+#define RSR_CCOUNT(r)	  asm volatile ("rsr %0,"__stringify(CCOUNT) : "=a" (r))
+#define WSR_CCOMPARE(x,r) asm volatile ("wsr %0,"__stringify(CCOMPARE)"+"__stringify(x) :: "a"(r))
+#define RSR_CCOMPARE(x,r) asm volatile ("rsr %0,"__stringify(CCOMPARE)"+"__stringify(x) : "=a"(r))
 
 static inline unsigned long get_ccount (void)
 {