board: rzg2l: Add RZ/G2L SMARC EVK board

The Renesas RZ/G2L SMARC Evaluation Board Kit consists of the RZ/G2L
System-on-Module (SOM) based on the R9A07G044L2 SoC, and a common SMARC
carrier board.

The ARM TrustedFirmware code for the Renesas RZ/G2L SoC family passes a
devicetree blob to the bootloader as an argument in the same was
previous R-Car gen3/gen4 SoCs. This blob contains a compatible string
which can be used to identify the particular SoC we are running on and
this is used to select the appropriate device tree to load.

The configuration renesas_rzg2l_smarc_defconfig is added to support
building for this target. In the future this defconfig will be extended
to support other SoCs and evaluation boards from the RZ/G2L family.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/arch/arm/mach-rmobile/Kconfig.rzg2l b/arch/arm/mach-rmobile/Kconfig.rzg2l
index 039d6b0..dc30bdf 100644
--- a/arch/arm/mach-rmobile/Kconfig.rzg2l
+++ b/arch/arm/mach-rmobile/Kconfig.rzg2l
@@ -9,6 +9,20 @@
 	help
 	  Enable support for the Renesas R9A07G044L (RZ/G2L) SoC.
 
+choice
+	prompt "Renesas RZ/G2L Family Board selection"
+	default TARGET_RZG2L_SMARC_EVK
+
+config TARGET_RZG2L_SMARC_EVK
+	bool "Renesas RZ/G2L SMARC EVK"
+	imply R9A07G044L
+	help
+	  Enable support for the RZ/G2L SMARC evaluation board.
+
+source "board/renesas/rzg2l/Kconfig"
+
+endchoice
+
 config MULTI_DTB_FIT_UNCOMPRESS_SZ
 	default 0x80000 if TARGET_RZG2L_SMARC_EVK