Fix incorrect timestamp assignment when writing inode
fix simplefs_write_inode to write the access time into disk_inode->i_atime and the modification time into disk_inode->i_mtime correctly.
After an inode has been modified or created, simplefs_write_inode(assigned to write_inode in simplefs_super_ops) is called to write the contents in the vfs inode to the relevant raw inode on disk. Because of a typo in simplefs_write_inode, i_atime gets assigned twice; once for writing access time, and again for writing modification time to it.
As a result, the raw inode metadata contains modification time on its access time field, and the modification time is never updated. Upon calling system calls like stat(), it returns modification time as access time, and an incorrect modification time(since it is never updated, and all bytes are zeroed out at mkfs, it defaults to 0, January 1st, 1970 in unix time).
Fix the assignments so access time is written to i_atime field and modification time is written to i_mtime field on on-disk inode structure.
Summary by cubic
Fixes incorrect timestamp assignment in simplefs_write_inode for kernel >= 6.7: write access time to disk_inode->i_atime and modification time to disk_inode->i_mtime instead of writing both to i_atime. Prevents i_mtime from being left zero so files report the correct modification time instead of 1970-01-01.