of: Rework linux/of.h and asm/prom.h include ordering

In preparation to prune things out of the Sparc, PowerPC and Microblaze
asm/prom.h files, change the #include statements to ensure that
even if asm/prom.h is included first, linux/of.h gets to determine the
order in which files are processed.

This patch adds a #include <linux/of.h> to each of the prom.h files
*above* the multi-include protection macros to ensure that linux/of.h
can define things before prom.h gets processed.

At the end of the merge the cross dependencies between the files should
be gone and a sane #include scheme can be restored.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Michal Simek <monstr@monstr.eu>
Acked-by: Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>