Convert CONFIG_CHIP_SELECTS_PER_CTRL to Kconfig

This converts the following to Kconfig:
   CONFIG_CHIP_SELECTS_PER_CTRL

Cc: Alison Wang <alison.wang@nxp.com>
Cc: Pramod Kumar <pramod.kumar_1@nxp.com>
Cc: Priyanka Jain <priyanka.jain@nxp.com>
Cc: Rajesh Bhagat <rajesh.bhagat@nxp.com>
Cc: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>