ARM: OMAP: Fix compile error if pm.h is included

Change the error to a warning.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/include/mach/pm.h

@@ -108,7 +108,7 @@
 	!defined(CONFIG_ARCH_OMAP15XX) && \
 	!defined(CONFIG_ARCH_OMAP16XX) && \
 	!defined(CONFIG_ARCH_OMAP24XX)
-#error "Power management for this processor not implemented yet"
+#warning "Power management for this processor not implemented yet"
 #endif
 
 #ifndef __ASSEMBLER__