Convert CONFIG_AT91_EFLASH to Kconfig

This converts the following to Kconfig:
   CONFIG_AT91_EFLASH

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Acked-by: Eugen Hristev <eugen.hristev@microchip.com>
diff --git a/configs/ethernut5_defconfig b/configs/ethernut5_defconfig
index 5d98318..7a701db 100644
--- a/configs/ethernut5_defconfig
+++ b/configs/ethernut5_defconfig
@@ -4,6 +4,7 @@
 CONFIG_ARCH_AT91=y
 CONFIG_SYS_TEXT_BASE=0x27000000
 CONFIG_SYS_MALLOC_LEN=0x121000
+CONFIG_AT91_EFLASH=y
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_ETHERNUT5=y
 CONFIG_NR_DRAM_BANKS=1
@@ -66,7 +67,6 @@
 CONFIG_GENERIC_ATMEL_MCI=y
 CONFIG_MTD=y
 CONFIG_MTD_NOR_FLASH=y
-CONFIG_USE_SYS_MAX_FLASH_BANKS=y
 CONFIG_MTD_RAW_NAND=y
 # CONFIG_SYS_NAND_USE_FLASH_BBT is not set
 CONFIG_NAND_ATMEL=y