mtd: cfi: enforce valid geometry configuration

mtd: cfi: enforce valid geometry configuration

MTD allows compile-time configuration of the possible CFI geometry
settings that are allowed by the kernel, but that includes a couple of
invalid configurations, where no bank width or no interleave setting
is allowed. These are then caught with a compile-time warning:

include/linux/mtd/cfi.h:76:2: warning: #warning No CONFIG_MTD_CFI_Ix selected. No NOR chip support can work.
include/linux/mtd/map.h:145:2: warning: #warning "No CONFIG_MTD_MAP_BANK_WIDTH_xx selected. No NOR chip support can work"

This is a bit annoying for randconfig tests, and can be avoided if
we change the Kconfig logic to always select the simplest configuration
when no other one is enabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>