exynos5: select HAVE_MONOTONIC_TIMER

We have the monotonic timer implemented on exynos now, and this
also enables helpful bootstage prints with timing info.

Change-Id: I3baa4c9d70d4b4d059abd5e05eddcabd5258dbfd
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/3210
Reviewed-by: Aaron Durbin <adurbin@google.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/cpu/samsung/Kconfig

@@ -1,5 +1,6 @@
 config CPU_SAMSUNG_EXYNOS5
 	depends on ARCH_ARMV7
+	select HAVE_MONOTONIC_TIMER
 	select HAVE_UART_SPECIAL
 	select DEFAULT_EARLY_CONSOLE
 	bool