[ARM] OMAP3 powerdomains: make USBTLL SAR only available on ES3.1 and beyond

Richard Woodruff writes that chip errata prevent USBTLL SAR from working
on OMAP3 ES levels before ES3.1:

http://marc.info/?l=linux-arm-kernel&m=123319614808833&w=2

Update the OMAP3 powerdomain structures appropriately.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>