console: avoid printing no or null time stamps

console: avoid printing no or null time stamps

During early boot timestamps aren't very useful, as they're all zero
(in "boot" mode) or absent altogether (in "date" and "datems" modes).
Log "boot" format timestamps when the date formats aren't available yet,
and log raw timestamps when boot ones are still all zero. Also add a
"raw" mode.

For the ARM side get_cycles() to produce a meaningful value, ARM's
cycle_t gets changed to uint64_t.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com>