arch/non-x86: Flip HAVE_MONOTONIC_TIMER default

Also remove allwinner/a10 dummy monotonic_timer
implementation.

Change-Id: I9dfa9b92dc63375465e3bb87b73eeefad601c810
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34112
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/cpu/qemu-power8/Kconfig

@@ -19,3 +19,4 @@ config CPU_QEMU_POWER8
 	select ARCH_VERSTAGE_PPC64
 	select ARCH_ROMSTAGE_PPC64
 	select ARCH_RAMSTAGE_PPC64
+	select NO_MONOTONIC_TIMER