RISC-V boards: Stop using the config string

RISC-V is moving towards OpenFirmware-derived device trees, and the old
functions to read the config string don't work anymore. Use dummy values
for the memory base and size until we can query the device tree.

Change-Id: Ice13feae4da2085ee56bac4ac2864268da18d8fe
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/21690
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/soc/lowrisc/lowrisc/cbmem.c

@@ -12,14 +12,15 @@
  */
 
 #include <cbmem.h>
-#include <commonlib/configstring.h>
 
 void *cbmem_top(void)
 {
 	uintptr_t base;
 	size_t size;
 
-	query_mem(configstring(), &base, &size);
+	/* FIXME: These values shouldn't necessarily be hardcoded */
+	base = 0x80000000;
+	size = 128 * MiB;
 
 	return (void *)(base + size);
 }