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>

src/arch/riscv/Makefile.inc

@@ -3,6 +3,7 @@
 ## This file is part of the coreboot project.
 ##
 ## Copyright (C) 2014 The ChromiumOS Authors
+## Copyright (C) 2018 HardenedLinux
 ##
 ## This program is free software; you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -82,8 +83,6 @@ romstage-y += \
 	$(top)/src/lib/memmove.c \
 	$(top)/src/lib/memset.c
 
-romstage-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
-
 # Build the romstage
 
 $(objcbfs)/romstage.debug: $$(romstage-objs)
@@ -116,8 +115,6 @@ ramstage-y += \
 
 $(eval $(call create_class_compiler,rmodules,riscv))
 
-ramstage-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
-
 ramstage-srcs += src/mainboard/$(MAINBOARDDIR)/mainboard.c
 
 # Build the ramstage

src/arch/riscv/include/stdint.h

@@ -73,4 +73,7 @@ typedef uint8_t bool;
 typedef s64             intptr_t;
 typedef u64		uintptr_t;
 
+/* FIXME: This is used in some print code and may be removed in the future. */
+#define PRIu64  "llu"
+
 #endif /* RISCV_STDINT_H */