We need to also have OFFPULLUDENABLE bit set to use the off mode pull values.
Otherwise the line is pulled down internally if no external pull exists.

This is has some documentation at:

http://processors.wiki.ti.com/index.php/Optimizing_OMAP35x_and_AM/DM37x_OFF_mode_PAD_configuration

Note that the value is still glitchy during off mode transitions as documented
in spz319f.pdf "Advisory 1.45". It's best to use external pulls instead of
relying on the internal ones for off mode and even then anything pulled up
will get driven down momentarily on off mode restore for GPIO banks other
than bank1.
Signed-off-by: Tony Lindgren <tony@atomide.com>