greybus: kernel_ver: add sg copy operations for kernel < 3.11

For older kernel, < 3.11, no copy to/from buffer with skip support was
defined. This could break builds for this versions of kernel.
Add them here.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Tested-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>