ARM: omap4: add platform specific info for GPMC and ELM controllers

This patch moves platform specific information for GPMC and ELM controller
into separate header files, so that any derivative devices do not mess other
header files.

Platform specific information added into arch-xx/../hardware.h
 - CPU related platform specific details like base-address of GPMC and ELM

Platform specific information added into arch-xx/../mem.h
 - Generic configs for GPMC and ELM initialization.
 - Hardware parameters or constrains specific to GPMC and ELM IP like;
   number of max number of chip-selects available

Signed-off-by: Pekon Gupta <pekon@ti.com>