arm64: kernel: compiling issue, need delete read_current_timer()

Under arm64, we will calibrate the delay loop statically using a known
timer frequency, so delete read_current_timer(), or it will cause
compiling issue with allmodconfig.

The related error:
  ERROR: "read_current_timer" [lib/rbtree_test.ko] undefined!
  ERROR: "read_current_timer" [lib/interval_tree_test.ko] undefined!
  ERROR: "read_current_timer" [fs/ext4/ext4.ko] undefined!
  ERROR: "read_current_timer" [crypto/tcrypt.ko] undefined!

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 6916b14ea140ff5c915895eefe9431888a39a84d)
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/arch/arm64/include/asm/timex.h b/arch/arm64/include/asm/timex.h
index b24a31a..81a076e 100644
--- a/arch/arm64/include/asm/timex.h
+++ b/arch/arm64/include/asm/timex.h
@@ -16,14 +16,14 @@
 #ifndef __ASM_TIMEX_H
 #define __ASM_TIMEX_H
 
+#include <asm/arch_timer.h>
+
 /*
  * Use the current timer as a cycle counter since this is what we use for
  * the delay loop.
  */
-#define get_cycles()	({ cycles_t c; read_current_timer(&c); c; })
+#define get_cycles()	arch_counter_get_cntvct()
 
 #include <asm-generic/timex.h>
 
-#define ARCH_HAS_READ_CURRENT_TIMER
-
 #endif