z_erofs_pcluster_readmore() may take a long time to loop when the page
offset is large enough, which is unnecessary should be prevented.
For example, when the following case is encountered, it will loop 4691368
times, taking about 27 seconds.
- offset = 19217289215
- inode_size = 1442672
Signed-off-by: Chunhai Guo <guochunhai@xxxxxxxx>