Pad config registers exist in APB_MISC_GP space, and control slew
rate, drive strengh, schmidt, high-speed, and low-power modes for
all of the pingroups in Tegra30. This builds off of the pinmux
way of constructing init tables to configure select pads (SDIOCFG,
for instance) during pinmux_init().

Currently, no padcfg entries exist. SDIO3CFG will be added when the
MMC driver is added as per the TRM to work with the SD-card slot on
Dalmore E1611.

Signed-off-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>