Convert CONFIG_CFI_FLASH_USE_WEAK_ACCESSORS to Kconfig

This converts the following to Kconfig:
   CONFIG_CFI_FLASH_USE_WEAK_ACCESSORS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/r8a77990_ebisu_defconfig b/configs/r8a77990_ebisu_defconfig
index 9470bee..0d8c9d5 100644
--- a/configs/r8a77990_ebisu_defconfig
+++ b/configs/r8a77990_ebisu_defconfig
@@ -68,6 +68,7 @@
 CONFIG_DM_MTD=y
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_CFI_FLASH=y
+CONFIG_CFI_FLASH_USE_WEAK_ACCESSORS=y
 CONFIG_FLASH_CFI_MTD=y
 CONFIG_SYS_FLASH_PROTECTION=y
 CONFIG_SYS_FLASH_CFI=y