OMAP2+: sdrc: fix compile break on OMAP4-only config on current omap-for-linus

On non-OMAP2 and non-OMAP3 kernel configs, turn omap2_sdrc_init() into
a no-op.  Otherwise, compilation breaks on an OMAP4-only config with
the current omap-for-linus branch:

arch/arm/mach-omap2/built-in.o: In function `omap2_init_common_devices':
../mach-omap2/io.c:421: undefined reference to `omap2_sdrc_init'

Thanks to Sergei Shtylyov <sshtylyov@mvista.com> for suggesting the use
of a empty static inline function rather than a macro.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
[tony@atomide.com: updated not to use __init for inline omap2_sdrc_init]
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/include/plat/sdrc.h

@@ -124,8 +124,14 @@ struct omap_sdrc_params {
 	u32 mr;
 };
 
-void __init omap2_sdrc_init(struct omap_sdrc_params *sdrc_cs0,
+#if defined(CONFIG_ARCH_OMAP2) || defined(CONFIG_ARCH_OMAP3)
+void omap2_sdrc_init(struct omap_sdrc_params *sdrc_cs0,
 			    struct omap_sdrc_params *sdrc_cs1);
+#else
+static inline void __init omap2_sdrc_init(struct omap_sdrc_params *sdrc_cs0,
+					  struct omap_sdrc_params *sdrc_cs1) {};
+#endif
+
 int omap2_sdrc_get_params(unsigned long r,
 			  struct omap_sdrc_params **sdrc_cs0,
 			  struct omap_sdrc_params **sdrc_cs1);