LU-14033 ldiskfs: Fix mballoc prefetch patch

LU-14033 ldiskfs: Fix mballoc prefetch patch

ext4-mballoc-prefetch patch was inadvertently broken during patch
rebasing.

In ext4_read_block_bitmap():
    ext4_read_block_bitmap_nowait() should not ignore locked

Test-Parameters: trivial
HPE-bug-id: LUS-9805
Fixes: fc87b01f96e8 ("LU-12477 ldiskfs: remove obsolete ext4 patches")
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I6ebe9dfe48f48706da3623e3d32d33dddf35b395
Reviewed-on: https://review.whamcloud.com/44894
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>