mtd: pxa3xx_nand: Remove dead code

This macro is not used anymore, so it's just dead code.
Remove it.

Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>