Fix #elif OPUS_ARM_INLINE_EDSP

Reported in https://github.com/xiph/opus/issues/108
diff --git a/celt/arch.h b/celt/arch.h
index c627a74..08b07db 100644
--- a/celt/arch.h
+++ b/celt/arch.h
@@ -160,7 +160,7 @@
 
 #ifdef OPUS_ARM_PRESUME_AARCH64_NEON_INTR
 #include "arm/fixed_arm64.h"
-#elif OPUS_ARM_INLINE_EDSP
+#elif defined (OPUS_ARM_INLINE_EDSP)
 #include "arm/fixed_armv5e.h"
 #elif defined (OPUS_ARM_INLINE_ASM)
 #include "arm/fixed_armv4.h"