mb/purism/librem_cnl: Drop selection of USE_LEGACY_8254_TIMER

It's not needed other than for booting w/SeaBIOS, where it is already
selected by default, and enabling it with edk2 payload prevents Linux/
Windows from fully entering S0ix.

TEST=build/boot purism/librem_cnl (Mini v2), verify Win11/Linux able
to enter and exit S0ix properly.

Change-Id: I974a82bedc4e06f48ce801f2bc0c29afbd80ffcf
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80602
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>

src/mainboard/purism/librem_cnl/Kconfig

@@ -13,7 +13,6 @@ config BOARD_PURISM_BASEBOARD_LIBREM_CNL
 	select SOC_INTEL_COMMON_BLOCK_HDA_VERB
 	select SPD_CACHE_IN_FMAP
 	select SPD_READ_BY_WORD
-	select USE_LEGACY_8254_TIMER
 
 config BOARD_PURISM_LIBREM_MINI
 	select BOARD_PURISM_BASEBOARD_LIBREM_CNL