video: tegra: 3d register read patch (see commit msg)

move 3d register read operations to the 3d device itself
and let 3d devices on tegra3 use direct to memory to read
the operations

Conflicts:
	drivers/video/tegra/host/gr3d/gr3d_t20.c
	drivers/video/tegra/host/host1x/host1x_channel.c
	include/linux/nvhost.h