staging: fsl-mc: delete prototype of unimplemented function

The function fsl_mc_bus_exists() has a prototype but is never
implemented so delete it from the header file.
Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-mc/include/mc-bus.h

@@ -91,8 +91,6 @@ void fsl_mc_init_all_resource_pools(struct fsl_mc_device *mc_bus_dev);
 
 void fsl_mc_cleanup_all_resource_pools(struct fsl_mc_device *mc_bus_dev);
 
-bool fsl_mc_bus_exists(void);
-
 void fsl_mc_get_root_dprc(struct device *dev,
 			  struct device **root_dprc_dev);