booting-without-of.rst is an ancient document that first outlined
Flattened DeviceTree on PowerPC initially. The DT world has evolved a
lot in the 15 years since and booting-without-of.rst is pretty stale.
The name of the document itself is confusing if you don't understand the
evolution from real 'OpenFirmware'. Most of what booting-without-of.rst
contains is now in the DT specification (which evolved out of the
ePAPR). The few things that weren't documented in the DT specification
are now.

All that remains is the boot entry details, so let's move these to arch
specific documents. The exception is arm which already has the same
details documented.

Cc: Frank Rowand
Cc: Mauro Carvalho Chehab
Cc: Geert Uytterhoeven
Cc: Michael Ellerman
Cc: Thomas Bogendoerfer
Cc: Jonathan Corbet
Cc: Paul Mackerras
Cc: Yoshinori Sato
Cc: Rich Felker
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: Borislav Petkov
Cc: "H. Peter Anvin"
Cc: x86@kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-mips@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Acked-by: Benjamin Herrenschmidt
Acked-by: Borislav Petkov
Acked-by: Michael Ellerman (powerpc)
Signed-off-by: Rob Herring