firmware: raspberrypi: print time using time64_t

The firmware timestamp is an unsigned 32-bit value, but we copy it into
a signed 32-bit variable, so we can theoretically get an overflow in
the calculation when the timestamp is between 2038 and 2106.

This changes the temporary variable to time64_t and changes the deprecated
time_to_tm() over to time64_to_tm() accordingly.

There is still an overflow in y2106, but that is a limitation of the
firmware interface, not a kernel problem.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>

drivers/firmware/raspberrypi.c

@@ -174,7 +174,7 @@ rpi_firmware_print_firmware_revision(struct rpi_firmware *fw)
 	if (ret == 0) {
 		struct tm tm;
 
-		time_to_tm(packet, 0, &tm);
+		time64_to_tm(packet, 0, &tm);
 
 		dev_info(fw->cl.dev,
 			 "Attached to firmware from %04ld-%02d-%02d %02d:%02d\n",