mtd: spi-nor: add TB (Top/Bottom) protect support

Some flash support a bit in the status register that inverts protection
so that it applies to the bottom of the flash, not the top. This yields
additions to the protection range table, as noted in the comments.

Because this feature is not universal to all flash that support
lock/unlock, control it via a new flag.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>