Convert CONFIG_SPL_DRIVERS_MISC et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_DRIVERS_MISC
   CONFIG_SPL_ENV_SUPPORT
   CONFIG_SPL_GPIO
   CONFIG_SPL_I2C
   CONFIG_SPL_LDSCRIPT
   CONFIG_SPL_LIBCOMMON_SUPPORT
   CONFIG_SPL_LIBGENERIC_SUPPORT
   CONFIG_SPL_LOAD_FIT_ADDRESS
   CONFIG_SPL_MMC
   CONFIG_SPL_NAND_SUPPORT
   CONFIG_SPL_NO_CPU_SUPPORT
   CONFIG_SPL_OS_BOOT
   CONFIG_SPL_POWER
   CONFIG_SPL_STACK_R
   CONFIG_SPL_STACK_R_ADDR
   CONFIG_SPL_WATCHDOG
   CONFIG_SPL_TEXT_BASE

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