quota: avoid time_t in v1_disk_dqblk definition

The time_t type is part of the user interface and not always the
same, with the move to 64-bit timestamps and the difference between
architectures.

Make the quota format definition independent of this type and use
a basic type of the same length. Make it unsigned in the process
to keep the v1 format working until year 2106 instead of 2038
on 32-bit architectures.

Hopefully, everybody has already moved to a newer format long
ago (v2 was introduced with linux-2.4), but it's hard to be sure.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/quota/quotaio_v1.h

···
 	__u32 dqb_ihardlimit;	/* absolute limit on allocated inodes */
 	__u32 dqb_isoftlimit;	/* preferred inode limit */
 	__u32 dqb_curinodes;	/* current # allocated inodes */
-	time_t dqb_btime;	/* time limit for excessive disk use */
-	time_t dqb_itime;	/* time limit for excessive inode use */
+
+	/* below fields differ in length on 32-bit vs 64-bit architectures */
+	unsigned long dqb_btime; /* time limit for excessive disk use */
+	unsigned long dqb_itime; /* time limit for excessive inode use */
 };
 
 #define v1_dqoff(UID)      ((loff_t)((UID) * sizeof (struct v1_disk_dqblk)))