x86/doc: Update documentation after file shuffling

While at it, also refer to the 32 bit entry file.

Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: linux-doc@vger.kernel.org
Cc: bpoirier@suse.de
Link: http://lkml.kernel.org/r/1418165684-6226-1-git-send-email-mcgrof@do-not-panic.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/x86/entry_64.txt

@@ -7,9 +7,12 @@ http://lkml.kernel.org/r/<20110529191055.GC9835%40elte.hu>
 The x86 architecture has quite a few different ways to jump into
 kernel code.  Most of these entry points are registered in
 arch/x86/kernel/traps.c and implemented in arch/x86/kernel/entry_64.S
-and arch/x86/ia32/ia32entry.S.
+for 64-bit, arch/x86/kernel/entry_32.S for 32-bit and finally
+arch/x86/ia32/ia32entry.S which implements the 32-bit compatibility
+syscall entry points and thus provides for 32-bit processes the
+ability to execute syscalls when running on 64-bit kernels.
 
-The IDT vector assignments are listed in arch/x86/include/irq_vectors.h.
+The IDT vector assignments are listed in arch/x86/include/asm/irq_vectors.h.
 
 Some of these entries are: