ARM: OMAP1: Make plat/mux.h omap1 only

We are moving omap2+ to use the device tree based pinctrl-single.c
and will be removing the old mux framework. This will remove the
omap1 specific parts from plat-omap.

Acked-by: Felipe Balbi <balbi@ti.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-usb@vger.kernel.org
Cc: linux-pcmcia@lists.infradead.org
Cc: spi-devel-general@lists.sourceforge.net
Signed-off-by: Tony Lindgren <tony@atomide.com>