configs: arc64: Switch to binutils Git submodule

The ARC64 binutils patches have been reworked so that it can be cleanly
applied on top of the upstream GDB 12.1 branch without affecting other
ARC architectures.

This commit updates the ARC64 toolchain configurations to use the
binutils Git submodule instead of the local ARC64-specific patch.

It also removes the local ARC64-specific binutils patch under the
`patches-arc64` directory since it is no longer used.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

configs/arc64-zephyr-elf.config

@@ -8,15 +8,8 @@ CT_ARCH_ARC=y
 CT_MULTILIB=y
 CT_ARCH_64=y
 CT_TARGET_VENDOR="zephyr"
-# FIXME: ARC64 binutils has a non-global patch (in patches-arc64), so we must
-#        use SRC_DEVEL to ensure that the patch gets applied. Eventually, the
-#        ARC64 binutils patch should be reworked so that it can be merged into
-#        the current Zephyr binutils branch without affecting other archs.
-CT_BINUTILS_SRC_DEVEL=y
-CT_BINUTILS_DEVEL_URL="https://github.com/zephyrproject-rtos/binutils-gdb.git"
-CT_BINUTILS_DEVEL_REVISION="c7d30a54fc17c1e9d9b1c39c7623222442c63af8"
-# CT_BINUTILS_SRC_CUSTOM=y
-# CT_BINUTILS_CUSTOM_LOCATION="${GITHUB_WORKSPACE}/binutils"
+CT_BINUTILS_SRC_CUSTOM=y
+CT_BINUTILS_CUSTOM_LOCATION="${GITHUB_WORKSPACE}/binutils"
 CT_NEWLIB_SRC_CUSTOM=y
 CT_NEWLIB_CUSTOM_LOCATION="${GITHUB_WORKSPACE}/newlib"
 CT_LIBC_NEWLIB_TARGET_CFLAGS="-O2"