Limitation i583: Self_Refresh Exit issue after OFF mode

Issue:
When device is waking up from OFF mode, then SDRC state machine sends
inappropriate sequence violating JEDEC standards.

Impact:
OMAP3630 < ES1.2 is impacted as follows depending on the platform:
CS0: for 38.4MHz as internal sysclk, DDR content seen to be stable, while
	for all other sysclk frequencies, varied levels of instability
	seen based on varied parameters.
CS1: impacted

This patch takes option #3 as recommended by the Silicon erratum:
Avoid core power domain transitioning to OFF mode. Power consumption
impact is expected in this case.
To do this, we route core OFF requests to RET request on the impacted
revisions of silicon.
Acked-by: Jean Pihet <j-pihet@ti.com>

[nm@ti.com: rebased the code to 2.6.37-rc2- short circuit code changed a bit]
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Eduardo Valentin <eduardo.valentin@nokia.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>