ext4: fix missing call to trace_ext4_ext_map_blocks_exit
ext4: fix missing call to trace_ext4_ext_map_blocks_exit

When ext4_ext_handle_uninitialized_extents(), we will directly return
from ext4_ext_map_blocks().  The trace point of
trace_ext4_ext_map_blocks_exit isn't called, and the user doesn't see
any result.  This patch tries to fix this problem.

Meanwhile in ext4_ext_handle_uninitialized_extents it returns errors
or the number of allocated blocks.  So 'ret' variable can be removed
due to previously modifications.

Signed-off-by: Zheng Liu <927570c33013ae711b16b2f69d88304bb3fcc969@taobao.com>

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