The SGX device on OMAP3 does not support retention, so remove RET from the
list of possible SGX power states.  Problem debugged by Richard Woodruff
<r-woodruff2@ti.com>.
Signed-off-by: Richard Woodruff <r-woodruff2@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>