ASoC: sof: Standardize ASoC menu

Current Kconfig menu at [ALSA for SoC audio support] has no rules.
So, some venders are using menu style, some venders are listed each drivers
on top page, etc. It is difficult to find target vender and/or drivers
because it is very random.

Let's standardize ASoC menu

Signed-off-by: Kuninori Morimoto <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Acked-by: Peter Ujfalusi <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/Kconfig

···
 source "sound/soc/rockchip/Kconfig"
 source "sound/soc/samsung/Kconfig"
 source "sound/soc/sdca/Kconfig"
-source "sound/soc/sof/Kconfig"
 source "sound/soc/spear/Kconfig"
 source "sound/soc/sprd/Kconfig"
 source "sound/soc/starfive/Kconfig"
···
 source "sound/soc/ux500/Kconfig"
 source "sound/soc/xilinx/Kconfig"
 source "sound/soc/xtensa/Kconfig"
+
+# SOF
+source "sound/soc/sof/Kconfig"
 
 # Supported codecs
 source "sound/soc/codecs/Kconfig"

sound/soc/sof/Kconfig

···
 # SPDX-License-Identifier: GPL-2.0-only
 menuconfig SND_SOC_SOF_TOPLEVEL
-	bool "Sound Open Firmware Support"
+	bool "Sound Open Firmware (SOF) platforms"
 	help
 	  This adds support for Sound Open Firmware (SOF). SOF is free and
 	  generic open source audio DSP firmware for multiple devices.