console: move search_device() from iomux.h to console.h

search_device() is defined in console.c. Move its declaration
to an appropriate header file.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/iomux.h

@@ -26,6 +26,5 @@ extern int cd_count[MAX_FILES];
 
 int iomux_doenv(const int, const char *);
 void iomux_printdevs(const int);
-struct stdio_dev *search_device(int, const char *);
 
 #endif /* _IO_MUX_H */