drivers: gnss: Fix snprintk return value check in gnss_dump

The snprintk function returns the number of characters that *would have
been* written if the buffer was large enough. This means if the return
value `ret` is greater than or equal to the buffer size `strsize`, the
output was truncated.

The existing check `(strsize < ret)` was incorrect as it did not
handle the case where `ret == strsize` (output fits exactly, but no
room for null terminator) and did not check for negative return values
which indicate an encoding error.

This commit corrects the check to `(ret < 0 || ret >= strsize)` to
properly detect truncation and errors, returning -ENOMEM in these
cases. This fix is applied to `gnss_dump_nav_data`, `gnss_dump_time`,
and `gnss_dump_satellite` functions.

Signed-off-by: Badr Bacem KAABIA <badrbacemkaabia@gmail.com>

Author: kaabia

drivers/gnss/gnss_dump.c

@@ -112,7 +112,7 @@ int gnss_dump_nav_data(char *str, uint16_t strsize, const struct navigation_data
 		       nav_data->speed / 1000, nav_data->speed % 1000,
 		       alt_sign, abs(nav_data->altitude) / 1000, abs(nav_data->altitude) % 1000);
 
-	return (strsize < ret) ? -ENOMEM : 0;
+	return (ret < 0 || ret >= strsize) ? -ENOMEM : 0;
 }
 
 int gnss_dump_time(char *str, uint16_t strsize, const struct gnss_time *utc)
@@ -124,7 +124,7 @@ int gnss_dump_time(char *str, uint16_t strsize, const struct gnss_time *utc)
 	ret = snprintk(str, strsize, fmt, utc->hour, utc->minute, utc->millisecond,
 		       utc->month_day, utc->month, utc->century_year);
 
-	return (strsize < ret) ? -ENOMEM : 0;
+	return (ret < 0 || ret >= strsize) ? -ENOMEM : 0;
 }
 
 #if CONFIG_GNSS_SATELLITES
@@ -138,7 +138,7 @@ int gnss_dump_satellite(char *str, uint16_t strsize, const struct gnss_satellite
 		       satellite->azimuth, gnss_system_to_str(satellite->system),
 		       satellite->is_tracked);
 
-	return (strsize < ret) ? -ENOMEM : 0;
+	return (ret < 0 || ret >= strsize) ? -ENOMEM : 0;
 }
 #endif