Define RAMTOP for x86 only

This Kconfig is deprecated, new platforms need to locate
ramstage stack in CBMEM instead.

Change-Id: I20ece297302321337cc2ce17fdef0c55242a4fc3
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/15189
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/mainboard/emulation/qemu-power8/Kconfig

@@ -44,10 +44,4 @@ config DRAM_SIZE_MB
 	int
 	default 32768
 
-# Memory map for qemu power8
-
-config RAMTOP
-	hex
-	default 0x1000000
-
 endif #  BOARD_EMULATION_QEMU_POWER8

src/mainboard/emulation/qemu-riscv/Kconfig

@@ -54,8 +54,4 @@ config DRAM_SIZE_MB
 # 0x0011_0000: CBFS data
 # 0x0100_0000: reserved for ramstage
 
-config RAMTOP
-	hex
-	default 0x1000000
-
 endif #  BOARD_EMULATION_QEMU_UCB_RISCV

src/mainboard/emulation/spike-riscv/Kconfig

@@ -54,8 +54,4 @@ config DRAM_SIZE_MB
 # 0x0011_0000: CBFS data
 # 0x0100_0000: reserved for ramstage
 
-config RAMTOP
-	hex
-	default 0x1000000
-
 endif #  BOARD_EMULATION_SPIKE_UCB_RISCV