Convert CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
   CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS

And we remove the entries from the README for a number of already
converted items.

Signed-off-by: Tom Rini <trini@konsulko.com>