pipe: Add DEV_PIPE_VFS_PATH to specify the pipe location

and put into /var/pipe by default like other pseudo device

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

drivers/pipes/Kconfig

@@ -34,4 +34,10 @@ config DEV_FIFO_SIZE
 		Sets the default size of the FIFO ringbuffer in bytes.  A value of
 		zero disables FIFO support.
 
+config DEV_PIPE_VFS_PATH
+	string "Path to the pipe device"
+	default "/var/pipe"
+	---help---
+		The path to where pipe device will exist in the VFS namespace.
+
 endif # PIPES

drivers/pipes/pipe.c

@@ -174,7 +174,7 @@ static int pipe_register(size_t bufsize, int flags,
 
   /* Create a pathname to the pipe device */
 
-  snprintf(devname, namesize, "/dev/pipe%d", pipeno);
+  snprintf(devname, namesize, CONFIG_DEV_PIPE_VFS_PATH"/%d", pipeno);
 
   /* Check if the pipe device has already been created */