clocksource: pass clocksource to read() callback

Pass clocksource pointer to the read() callback for clocksources.  This
allows us to share the callback between multiple instances.

[hugh@veritas.com: fix powerpc build of clocksource pass clocksource mods]
[akpm@linux-foundation.org: cleanup]
Signed-off-by: Magnus Damm <damm@igel.co.jp>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 641c8b6..604c1a3 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -33,7 +33,7 @@
 
 #include "fsyscall_gtod_data.h"
 
-static cycle_t itc_get_cycles(void);
+static cycle_t itc_get_cycles(struct clocksource *cs);
 
 struct fsyscall_gtod_data_t fsyscall_gtod_data = {
 	.lock = SEQLOCK_UNLOCKED,
@@ -383,7 +383,7 @@
 	}
 }
 
-static cycle_t itc_get_cycles(void)
+static cycle_t itc_get_cycles(struct clocksource *cs)
 {
 	u64 lcycle, now, ret;