f2fs: remove unnecessary tracepoint enabled check

There is no extra work before trace_f2fs_[dataread|datawrite]_end(),
so there is no need to check trace_<tracepoint>_enabled().

Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>