time: Fix signedness bug in sysfs_get_uname() and its callers

sysfs_get_uname() is erroneously declared as returning size_t even
though it may return a negative value, specifically -EINVAL.  Its
callers then check whether its return value is less than zero and indeed
that is never the case for size_t.

This patch changes sysfs_get_uname() to return ssize_t and makes sure
its callers use ssize_t accordingly.
Signed-off-by: Patrick Palka <patrick@parcs.ath.cx>
[jstultz: Didn't apply cleanly, as a similar partial fix was also applied
so had to resolve the collisions]
Signed-off-by: John Stultz <john.stultz@linaro.org>

kernel/time/clockevents.c

@@ -584,7 +584,7 @@ static ssize_t sysfs_unbind_tick_dev(struct device *dev,
 				     const char *buf, size_t count)
 {
 	char name[CS_NAME_LEN];
-	size_t ret = sysfs_get_uname(buf, name, count);
+	ssize_t ret = sysfs_get_uname(buf, name, count);
 	struct clock_event_device *ce;
 
 	if (ret < 0)

kernel/time/clocksource.c

@@ -909,7 +909,7 @@ sysfs_show_current_clocksources(struct device *dev,
 	return count;
 }
 
-size_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
+ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
 {
 	size_t ret = cnt;
 

kernel/time/tick-internal.h

@@ -31,7 +31,7 @@ extern void tick_install_replacement(struct clock_event_device *dev);
 
 extern void clockevents_shutdown(struct clock_event_device *dev);
 
-extern size_t sysfs_get_uname(const char *buf, char *dst, size_t cnt);
+extern ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt);
 
 /*
  * NO_HZ / high resolution timer shared code