Fix date output in x86 microcode driver.

The microcode stores its date in a uint32_t in some weird order
approximating pdp-endian. Rather than printing it like that, print it
properly in ISO standard form.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>