ARM: OMAP: Fix compile for OMAP_PM_NOOP if PM is not selected

Commit 6e740f9a (ARM: OMAP: Move omap-pm-noop.c local to mach-omap2)
moved omap-pm-noop to be local to mach-omap2. However, the makefile
entry got placed within ifeq ($(CONFIG_PM),y) which was not the
case earlier.

Fix the issue by moving it out of the ifeq ($(CONFIG_PM),y) in
the makefile as these stubs are needed also when PM is not set.

Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>