Add functions to access addresses in the device tree. These are brought
in from Linux 4.10.

Also fix up the header guard for fdtaddr.h to avoid confusion.

Signed-off-by: Simon Glass <sjg@chromium.org>

These support the flat device tree. We want to use the dev_read_..()
prefix for functions that support both flat tree and live tree. So rename
the existing functions to avoid confusion.

In the end we will have:

   1. dev_read_addr...()    - works on devices, supports flat/live tree
   2. devfdt_get_addr...()  - current functions, flat tree only
   3. of_get_address() etc. - new functions, live tree only

All drivers will be written to use 1. That function will in turn call
either 2 or 3 depending on whether the flat or live tree is in use.

Note this involves changing some dead code - the imx_lpi2c.c file.

Signed-off-by: Simon Glass <sjg@chromium.org>

Move this group of address-related functions into a new file. These use
the flat device tree. Future work will provide new versions of these which
can support the live tree.

Signed-off-by: Simon Glass <sjg@chromium.org>