ARM: OMAP2+: Fix undefined reference to set_cntfreq

If CONFIG_SOC_HAS_REALTIME_COUNTER is not selected for omap5
or dra7xx, we can get the following error:

arch/arm/mach-omap2/built-in.o: In function `omap4_secondary_init':
:(.text+0x7ab0): undefined reference to `set_cntfreq'

Fix the issue by not trying to initalize the realtime counter
unles CONFIG_SOC_HAS_REALTIME_COUNTER is selected.
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/omap-secure.h

@@ -76,6 +76,13 @@ static inline void omap_barrier_reserve_memblock(void)
 { }
 #endif
 
+#ifdef CONFIG_SOC_HAS_REALTIME_COUNTER
 void set_cntfreq(void);
+#else
+static inline void set_cntfreq(void)
+{
+}
+#endif
+
 #endif /* __ASSEMBLER__ */
 #endif /* OMAP_ARCH_OMAP_SECURE_H */