mb/google/brya: Allow variants to choose CAR setup configuration

Lists of changes:
1. Create choice config to let ADL mb variants to pick the desire CAR
setup configuration between NEM and eNEM, where NEM and eNEM Kconfig
have selected its required IA SoC common CAR Kconfig to able to perform
the early boot configuration using CAR.
2. Lists of variants (kano, redrix, and felwinter) to drop
INTEL_CAR_NEM Kconfig select and choose eNEM.
3. Default CAR configuration for ADL mb is still NEM due to still using
older SoC skus without eNEM support enabled.

BUG=b:168820083
TEST=Able to build and boot P2 boards using eNEM mode.

Change-Id: Ibe94e6b82739ec65829859271622d904d75e978d
Signed-off-by: subratabanik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59272
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: EricR Lai <ericr_lai@compal.corp-partner.google.com>

src/mainboard/google/brya/Kconfig

@@ -51,7 +51,6 @@ config BOARD_GOOGLE_BRYA_COMMON
 	select SOC_INTEL_ALDERLAKE_PCH_P
 	select SOC_INTEL_COMMON_BLOCK_PCIE_RTD3
 	select SOC_INTEL_CSE_LITE_SKU
-	select INTEL_CAR_NEM #TODO - Enable INTEL_CAR_NEM_ENHANCED
 
 config BASEBOARD_DIR
 	string
@@ -172,4 +171,19 @@ config HAVE_WWAN_POWER_SEQUENCE
 config USE_PM_ACPI_TIMER
 	default n
 
+choice
+	prompt "Cache as RAM (CAR) setup configuration to use"
+	default USE_ADL_ENEM if BOARD_GOOGLE_KANO || BOARD_GOOGLE_FELWINTER || BOARD_GOOGLE_REDRIX
+	default USE_ADL_NEM
+
+config USE_ADL_ENEM
+	bool "eNEM: when selected, the variant will use eNEM instead of regular NEM."
+	select INTEL_CAR_NEM_ENHANCED
+
+config USE_ADL_NEM
+	bool "NEM: when selected, the variant will use regular NEM."
+	select INTEL_CAR_NEM
+
+endchoice
+
 endif # BOARD_GOOGLE_BASEBOARD_BRYA || BOARD_GOOGLE_BASEBOARD_BRASK