For erofs_map_blocks() and erofs_map_blocks_flatmode(), the flags
argument is always EROFS_GET_BLOCKS_RAW.  Thus remove the unused flags
parameter for these two functions.

Besides EROFS_GET_BLOCKS_RAW is originally introduced for reading
compressed (raw) data for compressed files.  However it's never used
actually and let's remove it now.
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230209024825.17335-2-jefflexu@linux.alibaba.comSigned-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>