cpu: purge obsolete cpuid instruction support check

the `cpuid` instruction was introduced back in 1993 (according to
wikipedia). we can thus safely assume that this exists on all platforms we
care about.

this also removes the obsolete ability to bypass the level=0 check for
certain very old cpus.

src/misc/cpu.c

@@ -132,39 +132,11 @@ VLC_WEAK unsigned vlc_CPU_raw(void)
                   : "a" (reg) \
                   : "cc");
 # endif
-     /* Check if the OS really supports the requested instructions */
-# if defined (__i386__) && !defined (__i486__) && !defined (__i586__) \
-  && !defined (__i686__) && !defined (__pentium4__) \
-  && !defined (__k6__) && !defined (__athlon__) && !defined (__k8__)
-    /* check if cpuid instruction is supported */
-   asm volatile ("push %%ebx\n\t"
-                 "pushf\n\t"
-                 "pop %%eax\n\t"
-                 "movl %%eax, %%ebx\n\t"
-                 "xorl $0x200000, %%eax\n\t"
-                 "push %%eax\n\t"
-                 "popf\n\t"
-                 "pushf\n\t"
-                 "pop %%eax\n\t"
-                 "movl %%ebx,%1\n\t"
-                 "pop %%ebx\n\t"
-                 : "=a" (i_eax), "=r" (i_ebx)
-                 :
-                 : "cc" );
-
-    if( i_eax == i_ebx )
-        return 0;
-# endif
 
-    /* the CPU supports the CPUID instruction - get its level */
+    /* Get cpuid level */
     cpuid( 0x00000000 );
-
-# if defined (__i386__) && !defined (__i586__) \
-  && !defined (__i686__) && !defined (__pentium4__) \
-  && !defined (__k6__) && !defined (__athlon__) && !defined (__k8__)
     if( !i_eax )
         return 0;
-#endif
 
     cpuid( 0x00000001 );