greybus: fw-download: Create a macro for length of firmware file's name

Create a macro representing the length of the firmware file's name and
use that instead of using magic number in the code.
Suggested-by: Greg Kroah-Hartman <gregkh@google.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/fw-download.c

@@ -11,9 +11,12 @@
 #include "firmware.h"
 #include "greybus.h"
 
+/* Length of the string in format: ara_%08x_%08x_%08x_%08x_%s.tftf */
+#define FW_NAME_LEN		56
+
 struct fw_request {
 	u8			firmware_id;
-	char			name[56]; /* ara_%08x_%08x_%08x_%08x_%s.tftf */
+	char			name[FW_NAME_LEN];
 	const struct firmware	*fw;
 	struct list_head	node;
 };