ext2: introduce new flags argument for ext2_new_blocks()

This patch introduces a new flags argument for ext2_new_blocks() and also
a new EXT2_ALLOC_NORESERVE flag.

Signed-off-by: Ye Bin <yebin10@huawei.com>
Message-Id: <20230815112612.221145-3-yebin10@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>