fixed 2a4282f9 from https://gitee.com/arvinzzz/kernel_liteos_m/pulls/979

fix: The tm struct obtained by mktime lacks timezone information

BREAKING CHANGE:
The tm struct obtained by mktime lacks timezone information
变更API:
time_t mktime(struct tm *tmptr)
原先mktime从入参中获取时区信息进行计算，变更后tm结构体和返回值time_t的计算使用系统g_timezone时区环境变量。

Close I67UIA
Signed-off-by: Narvinzzz <zhaotianyu9@huawei.com>
Change-Id: I766cffbff3c1a25bb33cbd245225ee117909af3a

kal/posix/src/time.c

@@ -664,7 +664,7 @@ static time_t ConvertUtc2Secs(struct tm *tm)
     seconds += (tm->tm_mday - 1) * SECS_PER_DAY;
     seconds += tm->tm_hour * SECS_PER_HOUR + tm->tm_min * SECS_PER_MIN + tm->tm_sec;
 
-    seconds -= tm->__tm_gmtoff; // sub time zone to get UTC time
+    seconds += g_timezone;
     return seconds;
 }
 
@@ -690,7 +690,7 @@ time_t mktime(struct tm *tmptr)
     }
     timeInSeconds = ConvertUtc2Secs(tmptr);
     /* normalize tm_wday and tm_yday */
-    ConvertSecs2Utc(timeInSeconds, tmptr->__tm_gmtoff, tmptr);
+    ConvertSecs2Utc(timeInSeconds, -g_timezone, tmptr);
     return timeInSeconds;
 }