Memtest86+: fix potential integer overflow

Coverity spotted a case where a compiler could legally overflow a
uint32_t and produce incorrect results.

It wouldn't overflow unless delay() is called for over 4.29 seconds, but
why not fix it.  Add a uint64_t cast to ensure correct behavior.

Change-Id: Iab75d2a536066107f027db95023aeaa9eb6a678c
Signed-off-by: Ben Gardner <gardner.ben@gmail.com>
Found-by: Coverity (75584)
Reviewed-on: https://review.coreboot.org/14201
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
1 file changed