[HALX86] Re-enable HalpBiosDisplayReset() for x64: it actually supports display reset (#5513)

CORE-18185
Addendum to commit 215148267e7bad7

Everything that's needed (the x86 emulator with x86BiosCall) is implemented.
Fixes screen cleaning when bootvid takes over the VGA display.

hal/halx86/generic/x86bios.c

···
 NTAPI
 HalpBiosDisplayReset(VOID)
 {
-#if 0
     X86_BIOS_REGISTERS Registers;
     ULONG OldEflags;
     BOOLEAN Success;
···
     /* Restore previous flags */
     __writeeflags(OldEflags);
     return Success;
-#else
-    /* This x64 HAL does NOT currently handle display reset (TODO) */
-    return FALSE;
-#endif
 }
 #endif // _M_AMD64