hw: Move MARVELL_88W8618 Kconfig from audio/ to arm/

hw: Move MARVELL_88W8618 Kconfig from audio/ to arm/

The Marvell 88W8618 is a system-on-chip with an ARM core.
We implement its audio codecs and network interface.
Homogeneous SoC Kconfig are usually defined in the hw/$ARCH
directory. Move it there.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20220107184429.423572-2-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>