arm64: configs: Remove obsolete TI config

arm64: configs: Remove obsolete TI config

This config is causing conflicts with how fdtfile variable is
initialized.
For K3 devices, CONFIG_DEFAULT_DEVICE_TREE= "ti/k3-<board>.dtb".
With CONFIG_TI_FDT_FOLDER_PATH also prefixing "ti", fdtfile is then
"ti/ti/k3-<board>.dtb". This variable is updated when fitImage is
booted and fails to boot due to the parsing error "ti/ti/".

Given that there are no other users of this config other than K3 for
now, it is being removed.

Since am64x, j721e and j721s2 also define a DEFAULT_FDT_FILE, update
them to conform to the DEFAULT_DEVICE_TREE standard.

Signed-off-by: Aashvij Shenai <a-shenai@ti.com>