The i.MX31 SPI interface was refered by freescale as spi_ver_0_4 in one
of their older vendor extended linux releases. spi_ver_0_4 differs only
in minor aspects to spi_ver_0_7 (i.MX35) which is already supported by
barebox.
Regarding barebox, the differences boil down to the location and length
of the CHIP SELECT and BIT COUNT/BURST LENGTH elements of CONREG. The
spi_ver_0_4 variant is limited to single word bursts with a maximum of
32 bits_per_word.

Add support for the i.MX31 SPI interface to the barebox spi_ver_0_7
implementation.

Signed-off-by: Alexander Kurz <akurz@blala.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>