arch/riscv: Print the page table structure after construction

A new Kconfig option, DEBUG_PRINT_PAGE_TABLES, is added to control this
behaviour. It is currently only available on RISC-V, but other
architectures can use it, too, should the need arise.

Change-Id: I52a863d8bc814ab3ed3a1f141d0a77edc6e4044d
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/16015
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/arch/riscv/include/vm.h

@@ -63,7 +63,7 @@ size_t pte_ppn(pte_t pte);
 pte_t ptd_create(uintptr_t ppn);
 pte_t pte_create(uintptr_t ppn, int prot, int user);
 
-void walk_page_table(void);
+void print_page_table(void);
 
 void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, uintptr_t pageTableStart);
 void mstatus_init(void); // need to setup mstatus so we know we have virtual memory