block: add missed trace_block_plug
block: add missed trace_block_plug

After flush plug list, the list has no request, so we need to add a
trace_block_plug().

Signed-off-by: Shaohua Li <cb3904095a5bc20edc93ba3dfa3e7d27d981b654@intel.com>
Reviewed-by: Namhyung Kim <5c915a589b3ddf58cebf14bec41bcc143b37ac3c@gmail.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs