fs/erofs: Remove an unnecessary assertion

fs/erofs: Remove an unnecessary assertion

In [1] Sam points out an assertion does not hold true for 32-bit
platforms, which only impacts Large File Support (LFS) API usage
in erofs-utils according to Xiang [2]. We don't think these APIs
are used in u-boot and this restriction could be safely removed.

[1] https://lists.denx.de/pipermail/u-boot/2023-July/524679.html
[2] https://lists.denx.de/pipermail/u-boot/2023-July/524727.html

Fixes: 3a21e92fc255 ("fs/erofs: Introduce new features including ztailpacking, fragments and dedupe")
Signed-off-by: Yifan Zhao <zhaoyifan@sjtu.edu.cn>
Tested-by: Sam Edwards <CFSworks@gmail.com>