x86: Unify arch/io.h and arch/romcc_io.h

Here's the great news: From now on you don't have to worry about
hitting the right io.h include anymore. Just forget about romcc_io.h
and use io.h instead. This cleanup has a number of advantages, like
you don't have to guard device/ includes for SMM and pre RAM
anymore. This allows to get rid of a number of ifdefs and will
generally make the code more readable and understandable.

Potentially in the future some of the code in the io.h __PRE_RAM__
path should move to device.h or other device/ includes instead,
but that's another incremental change.

Change-Id: I356f06110e2e355e9a5b4b08c132591f36fec7d9
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/2872
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/lib.h

@@ -24,7 +24,7 @@
 #include <stdint.h>
 #ifndef __ROMCC__ /* romcc doesn't support prototypes. */
 
-#ifndef __PRE_RAM__ /* Conflicts with romcc_io.h */
+#ifndef __PRE_RAM__ /* Conflicts with inline function in arch/io.h */
 /* Defined in src/lib/clog2.c */
 unsigned long log2(unsigned long x);
 #endif