riscv/opentitan: Fix the ROM size

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reported-by: Damien Hedde <damien.hedde@greensocs.com>

hw/riscv/opentitan.c

@@ -25,12 +25,13 @@
 #include "hw/misc/unimp.h"
 #include "hw/riscv/boot.h"
 #include "exec/address-spaces.h"
+#include "qemu/units.h"
 
 static const struct MemmapEntry {
     hwaddr base;
     hwaddr size;
 } ibex_memmap[] = {
-    [IBEX_ROM] =            {  0x00008000,   0xc000 },
+    [IBEX_ROM] =            {  0x00008000, 16 * KiB },
     [IBEX_RAM] =            {  0x10000000,  0x10000 },
     [IBEX_FLASH] =          {  0x20000000,  0x80000 },
     [IBEX_UART] =           {  0x40000000,  0x10000 },