ARM: OMAP2: Change 24xx to use new register access

This patch changes 24xx to use new register access, except for clock
framework. Clock framework register access will get updates in the
next patch.

Note that board-*.c files change GPMC (General Purpose Memory Controller)
access to use gpmc_cs_write_reg() instead of accessing the registers
directly. The code also uses gpmc_fck instead of it's parent clock
core_l3_ck for GPMC clock.

The H4 board file also adds h4_init_flash() function, which specify the
flash start and end addresses.

Also note that sleep.S removes some unused registers addresses.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>