imx25: imx_spi: support CSPI v0.7 as found on i.MX25
Based on the Linux driver. Tested with m25p80 with CS in GPIO mode.
Clock setting support is ad-hoc as the corresponding mach is not using
the generic clock infrastructure.
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>