erofs-utils: lib: limit NONHEAD delta1 for compact indexes

erofs-utils: lib: limit NONHEAD delta1 for compact indexes

Otherwise it could be identified as a CBLKCNT lcluster.

It actually has no real impact for 4 KiB lclusters (blocks) since
EROFS_CONFIG_COMPR_MAX_SZ == 4 MiB and Z_EROFS_LI_D0_CBLKCNT means
2048 * 4KiB == 8 MiB.

Fixes: 0917ff150846 ("erofs-utils: fix delta[1] out-of-bound of compact indexes")
Fixes: 2f871035cca6 ("erofs-utils: mkfs: support compact indexes for bigpcluster")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250121130825.1722009-1-hsiangkao@linux.alibaba.com