purism/librem_skl: Improve boot time by enabling SPD Word Read

This speeds up the SPD read ('calling FspMemoryInit' phase) from
218ms to 134ms consistently.

Tested on both the Librem 13 v2 and Librem 15 v3.

Change-Id: I44fbe96c256972bd074537159771d61fe7adf082
Signed-off-by: Youness Alaoui <youness.alaoui@puri.sm>
Reviewed-on: https://review.coreboot.org/22969
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/mainboard/purism/librem_skl/Kconfig

@@ -8,6 +8,7 @@ config BOARD_PURISM_BASEBOARD_LIBREM_SKL
 	# Workaround for EC/KBC IRQ1
 	select SERIRQ_CONTINUOUS_MODE
 	select MAINBOARD_USES_FSP2_0
+	select SPD_READ_BY_WORD
 
 if BOARD_PURISM_BASEBOARD_LIBREM_SKL