acp_7_x: remove local xtensa config headers, use hal_xtensa

Remove the local copies of xtensa config headers for acp_7_x platform
as they are now provided by hal_xtensa module via Zephyr
(modules/hal/xtensa/zephyr/soc/amd_acp_7_3_adsp/xtensa/config/).

The SOC_TOOLCHAIN_NAME 'amd_acp_7_3_adsp' maps to the hal_xtensa
directory, making these local copies redundant.

Also remove the zephyr_include_directories() workaround for include/arch
path that was only needed to expose these local headers.

Signed-off-by: sneha-voona <sneha.voona@amd.com>

Author: sneha-voona