Accessing the IIM registers is cumbersome. The fuses are documented with
different register strides and there is no header file available, so the
different fields have to be read in the datasheets and translated into
the barebox format over and over again. This patch adds a header file
which has defines for the various fuses (for i.MX25 only so far, but
others can be added later) along with C functions to read/write the
fields.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>