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>
diff --git a/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig b/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig
index 2078af2..d9d1f8b 100644
--- a/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig
+++ b/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig
@@ -58,6 +58,7 @@
 CONFIG_BOOTFILE="uImage"
 CONFIG_DM=y
 CONFIG_DDR_CLK_FREQ=66666666
+CONFIG_CHIP_SELECTS_PER_CTRL=1
 CONFIG_SYS_BR0_PRELIM_BOOL=y
 CONFIG_SYS_BR0_PRELIM=0xEF001001
 CONFIG_SYS_OR0_PRELIM=0xFC000FF7