OMAP: powerdomain: Arch specific funcs for mem control

Define the following architecture specific funtions for omap2/3/4
.pwrdm_set_mem_onst
.pwrdm_set_mem_retst
.pwrdm_read_mem_pwrst
.pwrdm_read_prev_mem_pwrst
.pwrdm_read_mem_retst
.pwrdm_clear_all_prev_pwrst
.pwrdm_enable_hdwr_sar
.pwrdm_disable_hdwr_sar
.pwrdm_wait_transition
.pwrdm_set_lowpwrstchange

Convert the platform-independent framework to call these functions.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
[paul@pwsan.com: rearranged Makefile changes]
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Reviewed-by: Kevin Hilman <khilman@deeprootsystems.com>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>