staging: rtl8723bs: ensure cmd is large enough for %4s scanf format

char array cmd is being scanned in using a %4s scanf format
specifier and so cmd must be an array of 5 chars. Increase size
to 5 chars to ensure we don't have an overflow.

Detected with static analysis by cppcheck:

"(error) Width 4 given in format string (no. 1) is larger than
destination buffer 'cmd[4]', use %3s to prevent overflowing it."
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/os_dep/rtw_proc.c

@@ -295,7 +295,7 @@ static ssize_t proc_set_cam(struct file *file, const char __user *buffer, size_t
 	struct adapter *adapter;
 
 	char tmp[32];
-	char cmd[4];
+	char cmd[5];
 	u8 id;
 
 	adapter = (struct adapter *)rtw_netdev_priv(dev);