Add arm neon and mips dspr2 arch features

Current modules must use armv7_a_neon to specify source files that
compile only with neon.  If a future arch variant also supports neon,
all these modules will fall back to non-neon.  Support a neon arch
feature that modules can use instead.  Similarly, support dspr2 for
mips.

arm_device.go was also mixing armv7-a-neon with armv7_a_neon.  Use
armv7-a-neon consistently, and fix the - to _ when creating the
property structs.

Test: m -j checkbuild
Change-Id: I24d3764280ab3bcbb9a73c0934edc9b99fc7f6a0

android/arch.go

@@ -417,9 +417,11 @@ func createArchType(props reflect.Type) reflect.Type {
 		variants := []string{}
 
 		for _, archVariant := range archVariants[arch] {
+			archVariant := variantReplacer.Replace(archVariant)
 			variants = append(variants, proptools.FieldNameForProperty(archVariant))
 		}
 		for _, feature := range archFeatures[arch] {
+			feature := variantReplacer.Replace(feature)
 			variants = append(variants, proptools.FieldNameForProperty(feature))
 		}