am335x, guardian: mem: Add board dependent mem values

  - Add mem-guardian.h derived from am33xx/mem.h

    * Add GPMC config values optimized for Bosch Guardian Board
    * NAND Chip used by Bosch Guardian Board is Micron MT29F4G08ABBFA

Signed-off-by: Moses Christopher <BollavarapuMoses.Christopher@in.bosch.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210611161350.2141-3-Gireesh.Hiremath@in.bosch.com