On the enbw_cmc board is a KSZ8864RMN switch which needs
configured through spi before working. This is done on
startup from u-boot through a config file stored at an
address specified in the "hwconfig" environment variable,
subcommand "config".

For example on the enbw_cmc board:

hwconfig=switch:lan=on,pwl=off,config=0x60160000

The file has the following structure:

- a comment starts with a '#' or a ';' and ends with a newline
- The switch needs for its config a reg/value pair, so we
  have two columns in the file:
    reg  : contains the register address
    value: contains a 8 bit register value
  This 2 columns are seperated through space or tab.

example (minimal configuration on the enbw_cmc board):

;reg    value   comment
;-----------------------------------------
0x01	0x00
0x01	0x01    ; Start Switch with this configuration