staging: gdm72xx: Replace comparisons on jiffies values with wrap-safe functions

Fixes the following checkpatch.pl issue:

WARNING: Comparing jiffies is almost always wrong; prefer time_after,
time_before and friends

Signed-off-by: Michalis Pappas <mpappas@fastmail.fm>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>