ARM: OMAP2+: Update 81xx clock and power domains for default, active and sgx

These offsets seem to be common, so let's rename the defines. And let's
set up the default_l3_slow_81xx_clkdm with active and default powerdomains
for dm814x. These are needed for usb to work.

Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>