BACKPORT: erofs: rename utils.c to zutil.c

Currently, utils.c is only useful if CONFIG_EROFS_FS_ZIP is on.
So let's rename it to zutil.c as well as avoid its inclusion if
CONFIG_EROFS_FS_ZIP is explicitly disabled.

Signed-off-by: Chunhai Guo <guochunhai@vivo.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240401135550.2550043-1-guochunhai@vivo.com


Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Bug: 348591003
Change-Id: Iace477719fb803084955218a3e5ace74338f5ec8
(cherry picked from commit cacd5b04)
[Chunhai: Resolved minor conflict in fs/erofs/Makefile and
fs/erofs/utils.c ]
Signed-off-by: Chunhai Guo <guochunhai@vivo.com>