arm: mach-k3: am62ax: Move board selection to mach-k3

Currently each set of board targets from a vendor is selected inside
the board directory for that vendor. This has the problem of multiple
targets, one from each vendor, being selectable at the same time.
For instance you can select both TARGET_AM654_A53_EVM and
TARGET_IOT2050_A53 in the same build.

To fix this we need to move the target board choice to a common location
for each parent SoC selection. Do this in arch/arm/mach-k3.

Signed-off-by: Andrew Davis <afd@ti.com>
diff --git a/arch/arm/mach-k3/am62ax/Kconfig b/arch/arm/mach-k3/am62ax/Kconfig
new file mode 100644
index 0000000..c5f1ef8
--- /dev/null
+++ b/arch/arm/mach-k3/am62ax/Kconfig
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (C) 2023 Texas Instruments Incorporated - https://www.ti.com/
+#	Andrew Davis <afd@ti.com>
+
+if SOC_K3_AM62A7
+
+choice
+	prompt "K3 AM62Ax based boards"
+	optional
+
+config TARGET_AM62A7_A53_EVM
+	bool "TI K3 based AM62A7 EVM running on A53"
+	select ARM64
+	select BINMAN
+	imply BOARD
+	imply SPL_BOARD
+	imply TI_I2C_BOARD_DETECT
+
+config TARGET_AM62A7_R5_EVM
+	bool "TI K3 based AM62A7 EVM running on R5"
+	select CPU_V7R
+	select SYS_THUMB_BUILD
+	select K3_LOAD_SYSFW
+	select RAM
+	select SPL_RAM
+	select K3_DDRSS
+	select BINMAN
+	imply SYS_K3_SPL_ATF
+	imply TI_I2C_BOARD_DETECT
+
+endchoice
+
+source "board/ti/am62ax/Kconfig"
+
+endif