read_current_timer() cleanups

- All implementations can be __devinit

- The function prototypes were in asm/timex.h but they all must be the same,
  so create a single declaration in linux/timex.h.

- uninline the sparc64 version to match the other architectures

- Don't bother #defining ARCH_HAS_READ_CURRENT_TIMER to a particular value.

[ezk@cs.sunysb.edu: fix build]
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/timex.h

@@ -244,6 +244,8 @@ extern int do_adjtimex(struct timex *);
 /* Don't use! Compatibility define for existing users. */
 #define tickadj	(500/HZ ? : 1)
 
+int read_current_timer(unsigned long *timer_val);
+
 #endif /* KERNEL */
 
 #endif /* LINUX_TIMEX_H */