printk: fix printing of long long types

64-bit types were not being handled properly and depending on the
calling convention could result in garbage values being printed.

We still truncate these to 32-bit values, the predominant use-case
is printing timestamp delta values which generally fit in a 32-bit
value. However we are no longer printing random stuff.

Test case for printk() updated appripriately to catch this regression.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>