x86: correct OSXSAVE + AVX bit check

the result should have both bits set; previously this was converted from
webp incorrectly and resulted in a boolean check...

Change-Id: I2a7c7f2b491945f3a536ab4fca02247eccc892b8

vpx_ports/x86.h

diff --git a/vpx_ports/x86.h b/vpx_ports/x86.h
index 2a3ebbe..ae349fb 100644
--- a/vpx_ports/x86.h
+++ b/vpx_ports/x86.h
@@ -189,7 +189,7 @@
   if (reg_ecx & BIT(19)) flags |= HAS_SSE4_1;
 
   // bits 27 (OSXSAVE) & 28 (256-bit AVX)
-  if (reg_ecx & (BIT(27) | BIT(28))) {
+  if ((reg_ecx & (BIT(27) | BIT(28))) == (BIT(27) | BIT(28))) {
     if ((xgetbv() & 0x6) == 0x6) {
       flags |= HAS_AVX;