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
diff --git a/cc/config/mips_device.go b/cc/config/mips_device.go
index ccd60d6..42025a2 100644
--- a/cc/config/mips_device.go
+++ b/cc/config/mips_device.go
@@ -133,7 +133,11 @@
 		"mips32r2dsp_fp",
 		"mips32r2dspr2_fp",
 		"mips32r6")
-	android.RegisterArchFeatures(android.Mips, "rev6")
+	android.RegisterArchFeatures(android.Mips,
+		"dspr2",
+		"rev6")
+	android.RegisterArchVariantFeatures(android.Mips, "mips32r2dspr2_fp",
+		"dspr2")
 	android.RegisterArchVariantFeatures(android.Mips, "mips32r6",
 		"rev6")