x86: Add GDT descriptors for option ROMs

Option ROMs require a few additional descriptors. Add these, and remove the
enum since we now have to access several descriptors from assembler.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c
index cf421fa..30e5069 100644
--- a/arch/x86/cpu/cpu.c
+++ b/arch/x86/cpu/cpu.c
@@ -124,7 +124,7 @@
 {
 	struct gdt_ptr gdt;
 
-	gdt.len = (num_entries * 8) - 1;
+	gdt.len = (num_entries * X86_GDT_ENTRY_SIZE) - 1;
 	gdt.ptr = (u32)boot_gdt;
 
 	asm volatile("lgdtl %0\n" : : "m" (gdt));
@@ -144,10 +144,13 @@
 		     (ulong)&id->arch.gd_addr, 0xfffff);
 
 	/* 16-bit CS: code, read/execute, 64 kB, base 0 */
-	gdt_addr[X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff);
+	gdt_addr[X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x009b, 0, 0x0ffff);
 
 	/* 16-bit DS: data, read/write, 64 kB, base 0 */
-	gdt_addr[X86_GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff);
+	gdt_addr[X86_GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x0093, 0, 0x0ffff);
+
+	gdt_addr[X86_GDT_ENTRY_16BIT_FLAT_CS] = GDT_ENTRY(0x809b, 0, 0xfffff);
+	gdt_addr[X86_GDT_ENTRY_16BIT_FLAT_DS] = GDT_ENTRY(0x8093, 0, 0xfffff);
 
 	load_gdt(gdt_addr, X86_GDT_NUM_ENTRIES);
 	load_ds(X86_GDT_ENTRY_32BIT_DS);