posix-timers: Unify MONOTONIC and BOOTTIME clock behavior

Now that the MONOTONIC and BOOTTIME clocks are indentical remove all the special
casing.

The user space visible interfaces still support both clocks, but their behavior
is identical.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kevin Easton <kevin@guarana.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20180301165150.315745557@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/time/posix-timers.c

@@ -251,12 +251,6 @@ static int posix_get_coarse_res(const clockid_t which_clock, struct timespec64 *
 	return 0;
 }
 
-static int posix_get_boottime(const clockid_t which_clock, struct timespec64 *tp)
-{
-	get_monotonic_boottime64(tp);
-	return 0;
-}
-
 static int posix_get_tai(clockid_t which_clock, struct timespec64 *tp)
 {
 	timekeeping_clocktai64(tp);
@@ -1322,21 +1316,6 @@ static const struct k_clock clock_tai = {
 	.timer_arm		= common_hrtimer_arm,
 };
 
-static const struct k_clock clock_boottime = {
-	.clock_getres		= posix_get_hrtimer_res,
-	.clock_get		= posix_get_boottime,
-	.nsleep			= common_nsleep,
-	.timer_create		= common_timer_create,
-	.timer_set		= common_timer_set,
-	.timer_get		= common_timer_get,
-	.timer_del		= common_timer_del,
-	.timer_rearm		= common_hrtimer_rearm,
-	.timer_forward		= common_hrtimer_forward,
-	.timer_remaining	= common_hrtimer_remaining,
-	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
-	.timer_arm		= common_hrtimer_arm,
-};
-
 static const struct k_clock clock_monotonic_active = {
 	.clock_getres		= posix_get_hrtimer_res,
 	.clock_get		= posix_get_monotonic_active,
@@ -1350,7 +1329,7 @@ static const struct k_clock * const posix_clocks[] = {
 	[CLOCK_MONOTONIC_RAW]		= &clock_monotonic_raw,
 	[CLOCK_REALTIME_COARSE]		= &clock_realtime_coarse,
 	[CLOCK_MONOTONIC_COARSE]	= &clock_monotonic_coarse,
-	[CLOCK_BOOTTIME]		= &clock_boottime,
+	[CLOCK_BOOTTIME]		= &clock_monotonic,
 	[CLOCK_REALTIME_ALARM]		= &alarm_clock,
 	[CLOCK_BOOTTIME_ALARM]		= &alarm_clock,
 	[CLOCK_TAI]			= &clock_tai,