cper: add timestamp print to CPER status printing

The ACPI 6.1 spec added a timestamp to the generic error data
entry structure. Print the timestamp out when printing out the
error information.

Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
CC: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>