riscv: fix issues (timestrap & PRIu64)

When I tried to compile the RISC-V code (202e7d4f3c), I found some errors:
    `PRIu64` is undefined
    src/arch/riscv/timestamp.c does not exist

Currently RISC-V does not have the implementation and use of timestamp,
so I temporarily delete the code related to timestamp in the Makefile.
And define PRIu64.

Change-Id: I7f1a0793113bce7c1411e39f102cf20dbadda5d6
Signed-off-by: Xiang Wang <wxjstz@126.com>
Reviewed-on: https://review.coreboot.org/27543
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

0 files changed, 0 insertions, 0 deletions