fsp_broadwell_de: Select TSC_MONOTONIC_TIMER by default

This is currently selected by each derivative board's Kconfig even
though it's really an SoC-specific option.

Change-Id: Iad135261915a0857c53c18aaebde7e46c97a8f40
Signed-off-by: David Hendricks <dhendricks@fb.com>
Reviewed-on: https://review.coreboot.org/26344
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/fsp_broadwell_de/Kconfig

@@ -25,6 +25,7 @@ config CPU_SPECIFIC_OPTIONS
 	select HAVE_INTEL_FIRMWARE
 	select SMM_TSEG
 	select HAVE_SMI_HANDLER
+	select TSC_MONOTONIC_TIMER
 
 config CBFS_SIZE
 	hex