ASoC: xtensa: 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]
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/xtensa/Kconfig

···
 # SPDX-License-Identifier: GPL-2.0-only
+menu "Xtensa"
+
 config SND_SOC_XTFPGA_I2S
 	tristate "XTFPGA I2S master"
 	select REGMAP_MMIO
···
 	  Say Y or M if you want to add support for codecs attached to the
 	  I2S interface on XTFPGA daughter board. You will also need to select
 	  the drivers for the rest of XTFPGA audio subsystem.
+
+endmenu