[platform][pc] get working on legacy 386 PC

-Add support for x86 legacy mode, designed for 386+ instead of pentium+
-Fixup uart driver to support com2
-Stub out PCI driver properly
-Fixup IDE driver to detect legacy disks

arch/x86/thread.c

@@ -84,8 +84,10 @@ void arch_thread_initialize(thread_t *t)
     frame->rflags = 0x3002; /* IF = 0, NT = 0, IOPL = 3 */
 #endif
 
+#if X86_WITH_FPU
     // initialize the saved fpu state
     fpu_init_thread_states(t);
+#endif
 
     // set the stack pointer
     t->arch.sp = (vaddr_t)frame;