Replace #ifdef PIC checks with the more appropriate HAVE_EBX_AVAILABLE/HAVE_7REGS.

Originally committed as revision 19676 to svn://svn.ffmpeg.org/ffmpeg/trunk
diff --git a/libavcodec/msmpeg4.c b/libavcodec/msmpeg4.c
index 71de34c..8c0da0a 100644
--- a/libavcodec/msmpeg4.c
+++ b/libavcodec/msmpeg4.c
@@ -31,6 +31,7 @@
 #include "dsputil.h"
 #include "mpegvideo.h"
 #include "msmpeg4.h"
+#include "libavutil/x86_cpu.h"
 
 /*
  * You can also call this codec : MPEG4 with a twist !
@@ -647,7 +648,7 @@
        necessitate to modify mpegvideo.c. The problem comes from the
        fact they decided to store the quantized DC (which would lead
        to problems if Q could vary !) */
-#if ARCH_X86 && !defined PIC
+#if ARCH_X86 && HAVE_7REGS && HAVE_EBX_AVAILABLE
     __asm__ volatile(
         "movl %3, %%eax         \n\t"
         "shrl $1, %%eax         \n\t"