ASoC: Add macros for defining virtual enums

With the upcoming consolidation of normal MUXs and virtual MUXs we need to be
able to distinguish between enums with and without a backing register at the
enum level. Use the same approach as used for virtual mixer controls by setting
the reg field of the enum to SND_SOC_NOPM for enums without a backing register.
This patch adds a set of helper macros that can be used to define such enums.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

include/sound/soc.h

@@ -189,6 +189,8 @@
 	.mask = xmask, .items = xitems, .texts = xtexts, .values = xvalues}
 #define SOC_VALUE_ENUM_SINGLE(xreg, xshift, xmask, xnitmes, xtexts, xvalues) \
 	SOC_VALUE_ENUM_DOUBLE(xreg, xshift, xshift, xmask, xnitmes, xtexts, xvalues)
+#define SOC_ENUM_SINGLE_VIRT(xitems, xtexts) \
+	SOC_ENUM_SINGLE(SND_SOC_NOPM, 0, xitems, xtexts)
 #define SOC_ENUM(xname, xenum) \
 {	.iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname,\
 	.info = snd_soc_info_enum_double, \
@@ -293,6 +295,8 @@
 							ARRAY_SIZE(xtexts), xtexts, xvalues)
 #define SOC_VALUE_ENUM_SINGLE_DECL(name, xreg, xshift, xmask, xtexts, xvalues) \
 	SOC_VALUE_ENUM_DOUBLE_DECL(name, xreg, xshift, xshift, xmask, xtexts, xvalues)
+#define SOC_ENUM_SINGLE_VIRT_DECL(name, xtexts) \
+	const struct soc_enum name = SOC_ENUM_SINGLE_VIRT(ARRAY_SIZE(xtexts), xtexts)
 
 /*
  * Component probe and remove ordering levels for components with runtime
@@ -1092,7 +1096,7 @@ struct soc_mreg_control {
 
 /* enumerated kcontrol */
 struct soc_enum {
-	unsigned short reg;
+	int reg;
 	unsigned char shift_l;
 	unsigned char shift_r;
 	unsigned int items;