dmaengine/ARM: omap-dma: Fix the DMAengine compile test on non OMAP configs

The DMAengine driver for omap-dma use three function calls from the
plat-omap legacy driver. When the DMAengine driver is built when ARCH_OMAP
is not set, the compilation will fail due to missing symbols.
Add empty inline functions to allow the DMAengine driver to be compiled
with COMPILE_TEST.

Signed-off-by: Peter Ujfalusi <[e-mail]>
Signed-off-by: Vinod Koul <[e-mail]>

include/linux/omap-dma.h

···
 #define dma_omap15xx()	__dma_omap15xx(d)
 #define dma_omap16xx()	__dma_omap16xx(d)
 
+#if defined(CONFIG_ARCH_OMAP)
 extern struct omap_system_dma_plat_info *omap_get_plat_info(void);
 
 extern void omap_set_dma_priority(int lch, int dst_port, int priority);
···
 	return 0;
 }
 #endif
+
+#else /* CONFIG_ARCH_OMAP */
+
+static inline struct omap_system_dma_plat_info *omap_get_plat_info(void)
+{
+	return NULL;
+}
+
+static inline int omap_request_dma(int dev_id, const char *dev_name,
+			void (*callback)(int lch, u16 ch_status, void *data),
+			void *data, int *dma_ch)
+{
+	return -ENODEV;
+}
+
+static inline void omap_free_dma(int ch) { }
+
+#endif /* CONFIG_ARCH_OMAP */
 
 #endif /* __LINUX_OMAP_DMA_H */