erofs: enable sub-page compressed block support

Let's just disable cached decompression and inplace I/Os for partial
pages as the first step in order to enable sub-page block initial
support.  In other words, currently it works primarily based on
temporary short-lived pages.  Don't expect too much in terms of
performance.

Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231206091057.87027-6-hsiangkao@linux.alibaba.com