am335x, shc: add support for the am335x based bosch shc board

U-Boot SPL 2016.03-rc3-00019-g6dfb4c2-dirty (Mar 09 2016 - 07:40:06)
SHC C3-Sample
MPU reference clock runs at 6 MHz
Setting MPU clock to 594 MHz
Enabling Spread Spectrum of 18 permille for MPU
Trying to boot from MMC
reading u-boot.img
reading u-boot.img

U-Boot 2016.03-rc3-00019-g6dfb4c2-dirty (Mar 09 2016 - 07:05:35 +0100)

       Watchdog enabled
I2C:   ready
DRAM:  512 MiB
reloc off 1f783000
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
Net:   cpsw
U-Boot#

Signed-off-by: Heiko Schocher <hs@denx.de>