Use "select" to ensure that the required kconfig symbols are set
as expected.
Drop HOSTAUDIO since it is now equivalent to UML_SOUND.

Set CONFIG_SOUND=m in ARCH=um defconfig files to maintain the
status quo of the default configs.

Allow SOUND with UML regardless of HAS_IOMEM. Otherwise there is a
kconfig warning for unmet dependencies. (This was not an issue when
SOUND was defined in arch/um/drivers/Kconfig. I have done 50 randconfig
builds and didn't find any issues.)

This fixes build errors when CONFIG_SOUND is not set:

ld: arch/um/drivers/hostaudio_kern.o: in function `hostaudio_cleanup_module':
hostaudio_kern.c:(.exit.text+0xa): undefined reference to `unregister_sound_mixer'
ld: hostaudio_kern.c:(.exit.text+0x15): undefined reference to `unregister_sound_dsp'
ld: arch/um/drivers/hostaudio_kern.o: in function `hostaudio_init_module':
hostaudio_kern.c:(.init.text+0x19): undefined reference to `register_sound_dsp'
ld: hostaudio_kern.c:(.init.text+0x31): undefined reference to `register_sound_mixer'
ld: hostaudio_kern.c:(.init.text+0x49): undefined reference to `unregister_sound_dsp'

and this kconfig warning:
WARNING: unmet direct dependencies detected for SOUND

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Fixes: d886e87c ("sound: make OSS sound core optional")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: lore.kernel.org/r/202307141416.vxuRVpFv-lkp@intel.com
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-um@lists.infradead.org
Cc: Tejun Heo <tj@kernel.org>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: linux-kbuild@vger.kernel.org
Cc: alsa-devel@alsa-project.org
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Richard Weinberger <richard@nod.at>