Add more improvements for EEPROM.

Note :

NuttShell (NSH)
nsh> df
  Block  Number
  Size   Blocks     Used Available Mounted on
    64       16       16         0 /eeprom
   128      396      396         0 /etc
 32768    60281      720     59561 /fs/microsd
nsh>

Signed-off-by: cctsao1008 <chiacheng.tsao@gmail.com>