um/time: Fixup namespace collision

The new timer_setup() function for struct timer_list collides with a
private um function. Rename it.

Fixes: 686fef928bba ("timer: Prepare to change timer callback argument type")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Kees Cook  <keescook@chromium.org>

arch/um/kernel/time.c

@@ -98,7 +98,7 @@ static struct clocksource timer_clocksource = {
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-static void __init timer_setup(void)
+static void __init um_timer_setup(void)
 {
 	int err;
 
@@ -132,5 +132,5 @@ void read_persistent_clock(struct timespec *ts)
 void __init time_init(void)
 {
 	timer_set_signal_handler();
-	late_time_init = timer_setup;
+	late_time_init = um_timer_setup;
 }