coreinfo: Fix off-by-one in displayed month of year

According to C documentation, the range of tm_mon in struct tm is [0, 11].
Before the patch, the displayed month was indeed incorrect.

Change-Id: I9f95f1e978c45b3635e2edfe1ec496d7b0dec00a
Signed-off-by: Yasha Cherikovsky <yasha.che3@gmail.com>
Reviewed-on: http://review.coreboot.org/12438
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
1 file changed