adb: Improved detection of big endian architecture

Instead of testing for the (compiler specific) define
__ppc__ explicitly, use the define HAVE_BIG_ENDIAN provided by
AndroidConfig.h.  That way, it should work on all big endian
systems.

Change-Id: Ic4d62afcefce4c8ad5716178ebfcb2b055ac73ce
diff --git a/adb/transport_usb.c b/adb/transport_usb.c
index 2584163..ee6b637 100644
--- a/adb/transport_usb.c
+++ b/adb/transport_usb.c
@@ -27,8 +27,7 @@
 #include "usb_vendors.h"
 #endif
 
-/* XXX better define? */
-#ifdef __ppc__
+#ifdef HAVE_BIG_ENDIAN
 #define H4(x)	(((x) & 0xFF000000) >> 24) | (((x) & 0x00FF0000) >> 8) | (((x) & 0x0000FF00) << 8) | (((x) & 0x000000FF) << 24)
 static inline void fix_endians(apacket *p)
 {