coreinit/filesystem: Label HFIO/PCFS mount source type (#431)

* properly label PCFS mount type

now that we've got an open-source way of booting a cat-dev, and using
PCFS, we can confirm that this second mount source is indeed PCFS.

* fix one space

* pcfs -> hfio

Author: Mythra

include/coreinit/filesystem.h

@@ -192,8 +192,9 @@ typedef enum FSMediaState
 
 typedef enum FSMountSourceType
 {
-   FS_MOUNT_SOURCE_SD  = 0,
-   FS_MOUNT_SOURCE_UNK = 1,
+   FS_MOUNT_SOURCE_SD   = 0,
+   //! Devkit only API currently. Uses the PCFS channel to perform I/O operations on the attached host machine.
+   FS_MOUNT_SOURCE_HFIO = 1,
 } FSMountSourceType;
 
 typedef enum FSOpenFileFlags