configs: Add am62x_beagleplay_*_defconfig

Add am62x_beagleplay_* defconfig customized for the configuration of
BeaglePlay and drop the config fragments.

This is in preparation for dropping the dependency on ti vendor folder
entirely.

Signed-off-by: Nishanth Menon <nm@ti.com>
diff --git a/doc/board/ti/am62x_beagleplay.rst b/doc/board/ti/am62x_beagleplay.rst
index 44e728d..ea6c858 100644
--- a/doc/board/ti/am62x_beagleplay.rst
+++ b/doc/board/ti/am62x_beagleplay.rst
@@ -57,8 +57,8 @@
     :end-before: .. k3_rst_include_end_common_env_vars_defn
 .. prompt:: bash $
 
-  export UBOOT_CFG_CORTEXR="am62x_evm_r5_defconfig beagleplay_r5.config"
-  export UBOOT_CFG_CORTEXA="am62x_evm_a53_defconfig beagleplay_a53.config"
+  export UBOOT_CFG_CORTEXR=am62x_beagleplay_r5_defconfig
+  export UBOOT_CFG_CORTEXA=am62x_beagleplay_a53_defconfig
   export TFA_BOARD=lite
   # we dont use any extra TFA parameters
   unset TFA_EXTRA_ARGS