Merge branch 'master' of https://gitlab.denx.de/u-boot/custodians/u-boot-spi

- Enable DM_SPI on siemens omap boards (Jagan)
- Dropped some non-dm supported omap3 boards (Jagan)
- Dropped non-dm code in omap3 spi driver (Jagan)
- Dropped non-dm code in kirkwood spi driver (Bhargav)