The 'fs' shell command initializes media device with media type info,
but it's not able to initialize another controller of same media type.
Therefore, 'fs init' accepts device instance number.
ex) SATA(0), SATA device instance 1, hwpart 2, swpart 3
fs init 0:1 2 3
Signed-off-by: Aiden Park <aiden.park@intel.com>