arch: arm: mpu: update K_MEM_PARTITION_ macros for ARMv7-M

The ARM core MPU API now uses solely k_mem_partition_attr_t
objects to represent memory region attributes. The objects
now include all attribution properties (including cache-
ability and share-ability). This commit updates the macro
definitions to comply with the new ARM Core MPU standard.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>