ext4: make __ext4_block_zero_page_range() support large folio

ext4: make __ext4_block_zero_page_range() support large folio

The partial block zero range helper __ext4_block_zero_page_range()
currently only supports folios of PAGE_SIZE in size. The calculations
for the start block and the offset within a folio for the given range
are incorrect. Modify the implementation to use offset_in_folio()
instead of directly masking PAGE_SIZE - 1, which will be able to support
for large folios.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20250512063319.3539411-4-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>