libplatsupport: SPI on Exynos does not use a 180 degree phase feedback

[agacek]

The relevant code is here:

https://github.com/seL4/util_libs/blob/master/libplatsupport/src/mach/exynos/spi.c#L201

The comment says to use a 180 degree phase feedback, but the code sets no phase feedback. For a 180 degree phase feedback it should be v = (0x2 << FB_CLK_SEL_SHF);. The SPI for the CAN controller on the HACMS Odroid/daughterboard platform does not work correctly without a phase feedback (90, 180, or 270 would all work). Please set the phase feedback to 180 degrees or make it configurable when the SPI is initialized.

[agacek]

Fixed 808f1a0