RISC-V boards: Remove PAGETABLES section from memlayout.ld

RISC-V doesn't set up page tables anymore, since commit b26759d703
("arch/riscv: Don't set up virtual memory").

Change-Id: Id1e759b63fb0bc88ab256994d3849d16814affa0
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/25701
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/arch/riscv/include/arch/memlayout.h

@@ -19,7 +19,6 @@
 #define __ARCH_MEMLAYOUT_H
 
 #define STACK(addr, size) REGION(stack, addr, size, 4096)
-#define PAGETABLES(addr, size) REGION(pagetables, addr, size, 4096)
 
 /* TODO: Need to add DMA_COHERENT region like on ARM? */