FUSEs (OTP registers) can be written via /dev/imx-ocotp character device.

For example, writing MAC 12:34:56:78:9A:BC can be performed as
    > mw -l -d /dev/imx-ocotp 0x8c 0x00001234
    > mw -l -d /dev/imx-ocotp 0x88 0x56789ABC
and reading as
    > md -l -s /dev/imx-ocotp 0x88+8
    00000088: 56789ABC 00001234
, where 0x88 (0x22*4) and 0x8C (0x23*4) are offsets of MAC OTP registers.

Notice: FUSEs are PROM, so "0" (unprogrammed) bits
can be replaced with "1" (but not vice versa) only once.

Also, for MAC there are convinient parameters:
    > ocotp0.permanent_write_enable=1
    > ocotp0.mac_addr=12:34:56:78:9A:BC
    imx_ocotp 21bc000.ocotp: reloading shadow registers...
    imx_ocotp 21bc000.ocotp: reloading shadow registers...
    > echo $ocotp0.mac_addr
    12:34:56:78:9A:BC

Signed-off-by: Uladzimir Bely <u.bely@sam-solutions.net>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>